Neoprene wetsuit alternatives?

I have a severe neoprene allergy which makes wearing a wetsuit impossible, so the only tri I've done so far has been in a pool. I've tried to find neoprene alternatives and have been directed towards a manufacturer called "4th element" which makes 3mm suits for divers. However they're expensive and I don't want to buy a suit which isn't fit for purpose.Has anyone tried it out? Has anybody else suffered from a neoprene allergy and if so have you found an alternative that you can swim in/gives you enough buoyancy? I've tried Reed chillcheater rubberised fleece while sailing which basically becomes waterlogged and sinks you! Wearing a rash vest under a wetsuit doesn't protect me against the allergy. Any help/advice would be gratefully received. Thanks