I have checked out OBX as they have very good prices for torsen LSD's but zero option for the JZA80 supra. the previous generation yes, but that differential is different too. If your willing to fab mounts, i'd go with the gen III supra diff. LS400 diff is completely irs own, there are zero direct swaps for doing a quick swap.
I'm with ya, my 1991 LS needs one real bad and i would need to source a $1000 used supra diff/housing and then a custom driveshaft and them custom mounts. If your only taking it to the track... just weld it up. Its a big no-no for street use but at the track the negative aspects wont mean much since you need lock almost 100% of the time anyway.