Stroud Safety.
For a -5 it is not as critical, but Simpson is bad about not re-certing their stuff.
Impact makes some nice stuff, but they pissed off a bunch of racers when SFI pulled the cert on their -15 and -20 suits a few years ago due to counterfeit tags and did not make it right.
Stroud has been very consistent and taken care of me for years. First one I had made the resized a year or two later at no charge. (It shrank, yea, that's what happened)
There are cheaper fire suits, but is that really where you want to save money?