Try http://cascobaymolding.com in Maine. They’re good and fairly patient. Otherwise, gooogle away, and send emails to a bunch of factories. That’s how I found them in the first place. Another one I’ve heard good things about is http://www.premiersource.us. http://lusidarubber.com also specializes in silicone and pairs US sales team with Chinese factory, so it could be much cheaper than the other two, but I can’t vouch for their quality. Note that some molders are used to doing seals and gaskets, not cosmetic parts, and it may take a lot more work to get on the same page.
But do read up on designing for molding silicone, so you don’t waste much of your vendors’ time. It’s expensive but a fun material, and you don’t have to deal with the dreaded draft in many cases.