Whats the best adhesive to cover holes on an air mattress with a velvety top to it?

Unfortunately the holes need to be repaired from the inside. You can put a flexible adhesive and maybe even tape over the hole on the outside for a temporary fix, but the hole will widen from the inside when inflated and or deflated. Sorry to be the bearer of bad news but it's time for a new mattress. GOOD LUCK!!