I was on the same quest for awhile, looking for a Semi-dry. You might consider the Pinnacle Aquatics Semi Dry "Polar" 5-7-5 or the "Extreme" 6-8-6. The Merino wool lining really works well in fridgid conditions.
The Mares Isotherm is also another highly rated suit - many owners who have Mares and Pinnacles say the best you can get if your not going to dive dry in low 40's.
I was originally looking at the Henderson gold core 5-7-5, I hear they are great for a while, its easy to get in and out of comfortable and very warm - but several stories on frayed stichings complaints from many owners that they don't last.
Paul over at PG dive was very helpful & has very good pricing, will work with you online too - I'll give him the plug to return the favor because he really helped me out.
http://www.pgdive.com
Good luck - I know first hand how frustrating it is!
JC