http://www.petalia.com.au/templates/...?group_no=6050

Hagen is a good one, but you can find them way cheaper than that, thats just the first pic I came across.
Marshalls makes a good one too, looks just like the Hagen ones. I like the adjustable ones. But I prefer not to support Marshalls unless I have to.

Mine love the bell balls too, anything w/ bells.
I just said I heard of that cause I did. lol But personally I think as long as you don't have the collar on all the time he'll be just fine.