What about using the battery packs used in cordless drills / power tools like the De Walt 18V packs or Ryobi One systems?
Find a damaged drill and cut the base off to re use the socet, or just solder direct to the terminals and use a charge module to charge it up. You can buy the batteries separately too.
They are lightweight, have a good charge storage and are pretty rugged, so put up with a bit of pounding.
@sundberg84 Thank you so much for the advice, I knew that it would come down to small things here and there, and it's so much easier to tinker around in eagle than try to order a board, find the errors and fix/reorder over and over, so I appreciate it very much!
Time to get back in and make some changes 
@jbjalling Perfect, thank you so much for the confirmation! Time to get ordering
Capacitive switch sensor like the AT42QT1011 maybe?
Something along the lines of https://www.sparkfun.com/products/14520
Only thing I'm not sure of is whether the copper wire would trigger the capacitive sensor, although if its being inserted by hand then it should have a charge from your own bodies natural charge as well possibly? Or if it is being fed a charge by something else that is touching it, then it might be enough.