No idea where you can find the waterproof line here.
If I may recommand 4th element suits to you though, Livingseas carry them and they are the warmest suit in their respective categories: excellent value for money very little water penetration due to the technology of the seams between the neoprene panels and the wrist, neck and ankle seals while not being restraining, are very tight/ minimise water entry, the opportunity cost is they are a bit harder to don than other wetsuits but believe me it pays off.
The 3mm is as warm as a 5mm of other brands. I personally use the 5mm for diving in water temperatures ranging from 15 to 28 deg. celcius.
I'm not sure but I'd estimate the waterproof suits to be more expensive than 4th element