SF lines in general:
25mm:
Denizen
Ground Zero Games
MegaMiniatures
28-30mm
Hasslefree
Infinity
em-4
Urban Mammoth
Scotia/Grendel (several lines)
Rackham (the now discontinued AT-43 line; look at FFG and eBay)
Heresy
Mantic (upcoming releases for the Corporation faction)
Reaper (Chronoscape)
Hydra (check at Scale Creep, IIRC)
Blue Moon (from Old Glory, IIRC)
Others will be mentioned, I'm sure. I've not mentioned the 800lb gorilla (GW) because 1) they're sort of a given, and 2) their broadly useful SF is pretty thin on the ground.
Some of these lines will have vacc suited figures, others not. "Civilian" vacc suited figures are rather rare in any scale, frankly. Most figures suited for hostile environments are wearing hardsuits or blatant power armor. There are a few in the classic 50s look from Reaper and the line related to War Rocket, and the Blue Moon suited aliens are in combinations of hard/soft suits.
Some of the infinity line are in body stockings with enough headgear that they could be interpretted as vacc suits, but are typically heavily armed as well.
The only truly civilian suits I'm aware of are in 15mm from Ground Zero Games, which is out of your scale range.