Years ago there was one by Ashbass (I think) who was very insistsant that he made the only real ones or something.
I had one, sounded like a Mosrite Fuzzrite. GGG or BYOC has a $40 diy, and Catalinbread has one, as well as about everybody that makes a few fuzz pedals in their line.
Ennio fuzz-TGPr made, was really goid as well.
There's germanium and silicon versions. The Iron Butterfly sound is the silicon version. There are more than a few clones out there. I use the Fredric Effects Foxrite. It is priced low and sounds really good. It also has an additional boost stage at the output for much more volume than the original had.
The Ashbass is a clone of the Fuzzrite. If you want a better Fuzzrite, look into the Sanner / Hallmark Nu-Fuzz. Its a Fuzzrite at heart, but has an infinitely more useful tone control. Plus, Ed Sanner himself hand-wired the circuit.
Merkin gets my vote as well. I also a have a Basic Audio Zippy which is a Fuzzrite variant that isn't as aggressive but does a lot of other things. Just depends on how close you're looking to get to the original. Creepy Fingers is worth a look if you can find one.