Renaissance Dancewear is the best IMHO
http://renaissancedancewear.com/, but I don't know if they are in business anymore.
Shadow Dale Creations makes a good suit and neckseal.
http://www.shadowdalecreations.com/imperial.htm I love the built-in neckseal and it is very realistic looking, although the 1-size-fits-all suit is a little big on me and bunches up around the knees and arms. I'm 5'11" 170lbs.
TK-409 makes good neckseals.
http://www.tk409.com/tk409.html I would go for the smaller-ribbed version if he still offers it. The cloth that lines the bottom and goes over your shoulders tends to bunch up and go where it wants. I end up tucking all that inside my undersuit which is a pain.
You can also use a scuba dive SKIN, not suit. Just look out for any logos that might show.
And of course, underarmor, or a cheaper version of underarmor that you can find at wal-mart.
Gloves, you can go realistic and get rubber chemical gloves, or do like me and use nomex flight gloves. They are cloth with leather palms.
http://www.copquest.com/12-1500.htm