I don't know about GB1 but, if you're as much of a stickler for details as I am, this is what you want to look for for accurate looking GB2 boots…
http://www.jackal86.100megs8.com/mastertemp/Ghostbusters-Rel/im003205wg7.jpgAnyway, this style with the brass zippers, and “MAXITRED” soles. …I'm not sure if these are 100% accurate, but they look like dead-ringers for the screen-used boots to me.
Unfortunately, I do not know the brand of these boots. I found this pic during an internet search some time ago, and it wasn't accompanied with any useful information.
My brother-in-law has a pair of jump boots which I'm told are identical to these save for the fact that the zippers on his are painted black. His boots were manufactured by a company called “Carolina”.
Though it seems that several boot companies put MAXITRED or “Maxi-Tred” soles on their boots… so that doesn't seem to really point to a specific brand of jump boot.
It also seems the Caroline might not produce them anymore…
There is however another company called “Corcoran” that supposedly also / still produces jump boots with Maxi-Tred soles. I have yet to do any photo comparisons though.