I just bought a set of G36 side rails. I can't find it anymore on Taiwangun, looks like I got the last set.
Like THESE, only 2 pieces instead of 3.
Then I layed them on where I thought I wanted the VFG, scratched a small hole with a screwdriver. Then drilled a small hole with a powerdrill, then enlarged the hole with a drill that was just as wide as the screws. Only screws came with the set, no hex nuts. So searched some in the parts bin.
Same for the side rail.
The plastic seems more then solid enough to hold the VFG and even use it. If you wanted, you could place another rail on the bottom near the front sight, remove the stock bipod legs, and slap a Harris-style RIS mounted bipod on there. That would be cool I think.