If you are not looking for an exact match to an existing one, try calling Bill @ judge yachts. I know he offers a seat box with a livewell built in because his demo boat has it. Denton would be a lot faster and cheaper way to go; pick it up for a $6 toll and a tank of gas!
FWIW though, $400 for that box seems pretty reasonable. It's the freight and the wait that is a killer. Shipping by boat could easily take 2 months to get here!
Good luck with the search.