I have 24" Titan MaxRPMs. These provide more than enough support and I am sure my wrists would be thicker than yours. They have enough stretch that I can do them tight enough to lose all feeling in my hands. You can just loosely wrap them if you have excess left over. You only need a little bit of tension to get enough support. Too tight and I find it actually hinders raw benching, as you can't squeeze the bar as hard.
They only come in one smaller size, 50cm. The only reason I would go for the smaller ones is for squatting, as they are quicker to wrap and less likely to get in the way.
If you are getting wrist pain from benching, I would look closely at how you grip the bar as well.