WGB
I'm not sure about the boss covers. Are they just a cover? The Shimano one looks like the shifter attaches to it... if that's the case I don't think the stuff I print would take the higher stress (albeit others may disagree or use different material) Sorry I'm just not 100% sure.
The caps... I might need one to go off of as often there are little tolerance issues that come up from screen to print. Failing that, a few high res picture from different angles, and the vital measurements (if it plugs in, the diameter of the plug side, the outside, overall length / width - if it's threaded would also need the pitch/etc)