I've used one designed for an AR15 but don't remember what brand it was. All I had to do to make it work was drill another hole in the top of the carry handle on my AR10. The existing hole is too far back IIRC.
Eventually, that is exactly what I did and am much happier with it than I was the gooseneck.
I thought I had an old pic but this is the best I could do. It has the ALOSTYR handguards with the Aimpoint mounted directly on them. This setup worked great but was very front-end heavy.
As I mentioned, swapping the A2 upper for an A4 was the best answer IMHO.
Compact acog on carry handle.