You already mentioned all the options available in local companies .. I can't think of any other local brand ..
If you're planing to install this size in your GS then it'll be useless as GS is too heavy for this tyre size
I recently went to the Tyre market to replace my GS stock Tyre & i found these imported brands out there in 100/90/18
Dunlop (Rs.4500) DSI (Rs.3800) TVS (Rs.3800) Yokohoma Made in Japan (Rs.4500)
But finally i settled on DSI because it was the latest stock available in market .. (June 2013 manufactured) while Dunlop was 2010-2011 .. TVS was also fresh didn't like the shape of that tyre .. Don't know about Yokohoma