Re: 42" Vanity
It's possible, though not likely, that you can find a larger cabinet and cut it down to the size you need. To be honest, a custom cabinet isn't going to be much, if any, more expensive than the stuff you're going to find off the shelf at Evil Orange. I would contact a couple cabinet shops in your area to see what they'd charge for a basic 42" vanity.
Another option would be to reface the one you've got, which you could do yourself.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!