Geoff,
We use the Henderson Tri-Lam. They make both womens and mens models, here is a link:
Henderson TriLam suitsUnderneath we wear a fleece one-piece, the one I have was made to wear under a loose-fitting diving drysuit. Unfortunately you can't pull the TriLam over the fleece, the fleece-on-fleece might as well be velcro. So you need to add a slippery layer in between, I use a 4-way stretch lycra one-piece in between.
By the time you have the full setup, there is a serious cash investment. However, I would never go back once I tried it.
Paul