I measured my own out and had one made custom. It seemed custom to me but maybe not. I took about 5 measurements and filled out a little picture and faxed my order in. You might want to try that.
I'm out here in Sacramento. The shop was called Hot H2O and the owner's name is Dylan. I can't recall whom he ordered it through but I'm sure he can help out. Call him at 916-631-0505. Tell him Sean with the Black and Green Centurion sent you.