If you contact the host club of the regatta and they could probably set you up with a boat to use. It can get expensive to charter a boat, you can probably borrow one from the host club for that regatta.
Thanks. I found a boat to use at the Midwinters but was blown away by what Edison was asking for 3 days in a club boat. The Worlds charters are $250 (assuming I read the NOR correctly) and they are brand new boats. Let's just say the Mid Hosts quoted me almost double that for 3 days.