Here's another slouchy beret (you can leave off the pompom) http://kellymaher.wordpress.com/2007...beret-pattern/
It calls for using size 4 and 8s but you couldd use 8s and 10s. I've done one like it on 10 and 10.5s but only cast on about 64 sts.
You could also use the purl beret pattern, CO about half the sts. On size 10s with larger yarn you'd probably get 3.5sts/inch - half the 7sts on size 3s. And that would be a CO of 64, about what I used. Just use the inch measurements for the rest of the pattern.