The is a version of the 4eyes lens system bracket that obstructs the RGB lens less. It is not the latest bracket which is currently not available.
I would suggest lightly sanding it with a very fine sandpaper and then wiping it down with a damp cloth to remove dust, let it dry and spray it with one of the sprayable rubber coatings you can get on
Amazon, Home Depot or Lowes. Spray two coats, avoiding drips or pooling either on both inside and outside surfaces, but primarily surface to provide a grippable surface and also protect the Structure sensor from damage.
The 'Fujifilm DPC+3 Diopter Correction Lens for X-Pro1' lenses are little harder to obtain, and can be expensive. You may also look at the NIKON Japan Eyepiece Auxiliary Lens +3.0 which appears to be of similar diameter, but I have not actually tested it with this lens. The important thing is to find a lens with a
diopter of +3.
It should also be noted that the Occipital Structure apps for iOS do not support a distance less than 400mm so the lens system cannot be used with an iOS app like itSeez3D. If you are developer, you can contact Occipital to see if this has been corrected in their SDK. If not, suggest that it should be. You will also need to correct for the lens distortion that creates a slight bow in flat surfaces. This curvature also creates problems in stitching in larger objects. It also should be noted that this does not increase the resolution of the scanner and small objects with thin extensions will not capture well.
This does work with Occipital's PC based product 'Scanect' and can be used with an iOS device if you use it in WiFi remote mode. If you purchase it with the seperate hacker's cable with USB, it can be used with a laptop.
NOTE: This device works by decreasing the focal length allowing you to get closer to the object being scanned. It does not increase resolution or mesh desiity. It also narrows the range of effective scanning to 300mm -25mm +50mm. This does require more patience and awareness of how far the sensor is from the object. I personally have seen noticeble differeces in facial scans using the lens. I have several scans on
Sketchfab that bear this out.
Here is a tutorial on its use on the
All Things 3D YouTube channel: