The only compatible bolt for that back block is the one you have.
You can, though, put a standard 2000 style back block on it, and use any 2000 stly bolt. There will be a gap, though, so it won't look quite as cosmetically pleasing.
An unmatched back block that will leave a cutout in the body and look, cosmetically speaking, like crap and cost at least $30 is less complicated than breaking out the drill bits and making a hole?