Check eBay.
I've bought many from there for less than $10.
The one you need is the one for a metal CP. Vs, punchout, DK3, MB. It's the one that has a black plastic plate and small, thick (1/8"?) washer and no clear ring. Also, make sure it has a four way restrictor and not an eight or two way. Those can be bought at Mikes.