I eyeballed this measures , they are right ? Does it fit this backs ?! http://www.aliexpress.com/item/15851-Free-Shipping-Wholesale -Silver-Iron-Earring-Back-100PCS/1452506443.html ?!
The materials from Shapeways may be harmful to be used as earrings. It may be better to use these instead and attach them to your design. http://www.aliexpress.com/item/18223-Free-Shipping-Wholesale -ball-3MM-Silver-Copper-Steel-Needle-Ball-Stud-Earring-20PCS -with/1452382884.html
I`m a very allergic person myself but ... the fact it is that I`m 1% of globe population so ... Not all people are born with my defects , good part it is that some that have my defects are international stars.
Here one can find some good information on the subject. And a good place to go for findings is Rio Grande.