Default Please help! I can't figure this out

Hey everyone. I have a SPH-L900 and I was running rooted 4.1.2 stock rom. I was rooted to run wifi tether. I updated to 4.3 unknowing that I would lose the ability to use my Trev-E Wi-Fi tether.
I have been looking for the 4.1.2 .tar to back date but the ones I find either don't work when I try to flash through Odin V. 3.04 or the link is just no good. Is there a way to get free wifi tether with 4.3 that I'm unaware of?
I've tried the Mod and that didn't work.
Otherwise what am I doing wrong with trying to back date to 4.1.2 and where can I get a working copy of the 4.1.2 .tar?
Any and ALL help greatly appreciated!
Wes~