Don't automatically assume he is a wimp. If I bundle mine up warm enough they head out and roll in the snow. I have to keep a towel by the door...
Potty train NOW so that he learns to make quick trips outside. Mine run out there and pee and come right back. Coats that cover the belly are better than the ones that just velcro at the chest and belly.
THESE are my favorite. Gooby makes good coats too.