Hi, I’ve developed a GPS tracking device for my dog. Just records where he’s been and keeps track of his top speed and distance travelled and whatnot. I currently have this crammed into a plastic box that I put into a side pocket on his tactical vest. I’d really like to reduce this to something that can just fit on his collar. Right now its using a Thing Plus C and a GPS qwiic board. I think these could both fit into some kind of flexible container that could follow the curve of the collar. Anybody know of such a thing or have any other container ideas?
You could get some large heat-shrink and wire the boards where they are all wired/arranged ‘longways’…seal it and strap it to the collar 
A dog’s collar is sort of a small form-factor; which almost dictates making your own custom board instead of using proto boards. Pre-made stuff would seem to favor platforms like the LilyPad or CircuitPlayground. Maybe using parts of the LilyPad series (e.g. power, threads) along with a custom board. If sticking with the boards you have, you could conformal coat them and then sew them on to the collar. Another option would be to 3D print some custom enclosure that molds to the collar (perhaps out of TPU - though I do not know how good TPU would be for waterproofing).
Useful links associated with items above:
https://www.sparkfun.com/lilypad_sewable_electronics
https://www.adafruit.com/product/3000