We were scared to drill holes in our new TT as well, But after the first, it was nothing for the rest. LOL!
We used pop toggles that are made for thin drywall, they hold 50lbs. Not sure, I need that much, but they work great for the TT walls, We used them for the TP holder, hand towel holder and we hung a hanging shoe holder on the back bathroom wall to hold everything. And it holes it up just fine with everything in there.
You have to drill a hole, use a drill stop so you dont go though the wall. Then fold it so its bent in half in the center, insert in the hole, use the popping pin that comes with it, then screw in your TP holder.