Hello there,
Shapeways has nice machines (SLS, SLA...) that can do stuff typical home FDM/FFF printers using plastic fillament can not do, but the price for parts are higher then the typical DIY prints. 15-30€/12-24gbp per Kilogram ABS or PLA.
There even is rubbery PLA now, so it would really be possible.
Some eypieces I have come with hard plastic caps, and those should definitely be possible to print.
Only things I could find so far is http://www.thingiverse.com/thing:8450
and
https://www.thingiverse.com/tag:lens_cap
I allready thought about printing some eyepiece caps as I lost a few. But my printers are currently standing in the school I teach 3d printing at, so I do not get to print as frequently as I used to :-)
I did print a bunch of things for astronomy, camera adapters and such,
http://www.thingiverse.com/thing:10897
http://www.thingiverse.com/thing:13922
http://www.thingiverse.com/thing:19212
...and as soon as I get around to it, I will print some eyepiece covers.
I quickly estimated the printing cost of a bottom cover: 4-5 Cent :-)