I believe the rule is if the water is 75 fh or less wetsuits are allowed. Most dive shops will rent a wetsuit. Some of the larger ones may even have tri specific suits. Just tell them what you want it for and they will help you out. I have rented wetsuits locally (Tucson)for tris with ocean swims with no problem. Even though I had the suit thurs- mon they only charged me for 1 day since I was only using for 1 day. $20 is a lot different than spending $200 for a suit to use 1-3 times a year.
If you are talking rent a scuba wetsuit rental, a store in Dallas, TX (I am not affiliated, just purchased all my scuba gear there) has an online site. They sell some Neosport 3/2mm full wetsuits for around $80 - they travel great. Taken mine to Australia, Mexico, and Florida. www.scubatoys.com
I am hesitant to rent wetsuits, you know they say there are two kinds of divers, those that pee in their wetsuits and those who do not admit they do....