Try DesignSpark Mechanical or Fusion 360. Both are free to download and use. If you use DesignSpark Mechanical keep in mind there is no 3D mirror command because it is the free reduced function version of SpaceClaim. In DesignSpark Mechanical you would have to use the 3D mirroring as you drew the parts in 2D to be extruded in 3D later on.
There are numerous ways to make this in 3D including using 3D scanning. Here's the process I would use in DesignSpark Mechanical. I would take a photo of the large side; to do that I'd have the camera a long way away and zoom in so as to prevent as much lens distortions as possible. I'd lay a ruler on it before taking the photo so I'd could use that as a photogramaetry refernce. Then I'd do the same for the small side.
I'd load the image large side image in DesignSpark Mechanical in the 2D mode and I'd draw a line on the ruler that was in alignment with the ruler. I'd then extend the line so that it was the same length as the ruler. I'd then scale the image so that the length of the line and the length of the ruler were the same. At that point, anything I wanted to draw would be the correct scale.
What I'd do then is basically trace out the holes and the outer contours of the part in the photo. Before I started drawing though I'd create a mirror line so whatever I drew would automatically make a mirror of everything I drew. This is because you need to have a mirror copy in the end.
I'd then go to 3D mode and that would automatically make my bounded lines into a surface.
Then I'd put that surface on a layer so I could turn the visibility of the layer off and on.
Then I do all of that exactly the same for the small side photo. In the scaling step I'd use the large side photo as a guide for scaling and alignment of the small side photo. I'd also flip the photo 180 degrees if needed to make sure the correct side was facing the viewport. DesignSpark Mechanical lets one vary the transparency of a photo so that it can easily be scaled and aligned by looking through the photo to references below.
Once I had the small and the large surfaces I'd take a measurement of the width of the actual part and I'd move one of the surfaces away from the other by that measurement amount. Then I'd go to 2D mode and I'd look at it from one of the ends and draw the profile with a wall thickness measurement of the actual part to get the wall thickness correct. Also, using a radius gauge I'd take radius measurements of the curved edges of the part. Once I had the profile drawn up in 2D I would extrude it using the sweep command of the pull tool. In doing that I'd use the edges of the surfaces as guides to constrain the sweep to the shape of the part. Then I'd repeat the process for the mirrored side.
At that point, the 3D models of the two parts would be finished but it would need the lettering. I would find a TrueType font that matches the lettering on the part and then type out the lettering, project the letters onto a surface, and then delete the surrounding surface to leave just the letters. Then I'd make a copy of the letters and rotate them 180 degrees for the mirrored side. I'd then move the letters to the center of the part and use one of the edges to move them along the edge using the move along trajectory of the move tool to make the letters match the curvature of the part. From there I'd project the letters to the surface and then extruded the letters outward to make them into 3D. To finish up I'd add the lettering to the large side and do the lettering on the mirrored model and then export as an STL file for uploading to Shapeways.
Your two parts look simple but they are somewhat advanced when comes to the 3D modeling techniques that will be needed to to make them in 3D. What I described might not work perfectly when it comes to sweeping the profile and have it be constrained properly. So, if that happened one would need to try making it another way and if that didn't work yet another way would need to be tried. It could end up being a can of worms if you tried to do it yourself since you'd have such a large learning curve to get everything right. If you want to get into 3D modeling then go for it because it would be a good way to learn 3D modeling. However, if you just want to get the 3D printed parts in your hands then I'd take Frozenrain's suggestion and hire a designer to do the work. You can contact them directly
here. Or, you can make a post
here describing what you need like you have and you'll get lots of quotes.
What are you ultimately trying to do? Do you just need a copy of these parts and you want to do that via 3D printing or do you want to market this as a product?