You can rent suits, though it might be difficult to find one as ugly as the G-Man's
.
As for teh HEV and Armor, find a vest for the armor, make some cardboard-ish little round pad things, draw teh BM logo and 'SECURITY' on the back, make a nametag, etc etc., and for the HEV, find some cardboard, make the shape, and spraypaint it orange?
The SD Gman looks cooler. (or one of the many...) His eyes are bloodshot and it looks creepy. The Science and Industry update SD administrators look cool...id like a G-man with HL textures on that model.