i trust you animal loving crafters to use the clicker responsebly, there's some really good info tuts in Emily's channel http://www.youtube.com/watch?v=Bs_M9Fzc94U
i made (2) from plastic bottle and it's cap
use the curved part of the bottle for the clicking part (not too curved though 'cuz then it won't pop)
cut slits on both sides of the cap, insert the plastic (it's a bit tricky here, use the tip of the knife to guide the plastic sheet, also try making the slit you gonna insert to a bit wide)
and ... that's about it.
adjust it a bit and stuff, you can apply glue or tape to the side,
make sure to not trim a lot so it wont slip out of the slits, you know what i mean?
also i noticed that the smaller cap clicker pops back better.
don't fall in the trap that bigger is louder.
if you're interested there a short demo video of them 2 on my blog
hope it'll do you good,
take care of your dog!
c, c & q