I'd check out Icefalcon, as well as the GDFB options on KoA (the mouse-over glossary should be working for those abbreviations).
What you're looking for is a long-sleeve hauberk. The term "haubergeon" means a shorter, half-sleeved mail shirt, whereas "hauberk" is the longer, full-sleeve version.
To know what size you need, you need to start with whatever under-garments you'll use (such as a gambeson or aketon), and get a chest measurement over that. Then add at least 4 inches, preferably 6.
Keep in mind it's easier to resize mail downward than upward. It's also easier to grow into mail that's too big, than to lose a bunch of weight and keep it off as you get older.