If you look at the Stephanie and Tim finished bath thread you can see the lookalike they bought from Amazon. I think it was called the Beverly. I'll post a link to another online company I found through another post, though I'm not sure it's in the price range you're looking for.

If you're looking for a cabinet only, instead of the kind that comes with sink, top and faucets, I highly recommend Barker Cabinets. You can order the RTA cabinets to your exact dimensions, and the quality is great. But you'll have to assemble and paint them. I did my kitchen with their Shaker cabinets, painted white, and have no regrets.

Here is a link that might be useful: RH look-alike vanity