easiest reverse option might be that collapsible paddle, you use to paddle backwards
3 seaters and jetboats had reverse gates. 2 seaters didn't .
You could put on a reduction/stering nozzle with reverse and plumb the wire in through your hull and install the pull bar to your console but it will be a bit of trouble and you'll loose your trim option.
you'd need GTS/GTX reduction steraing nozzel, the springs, the cable, the post/grab handle
same vintage 3 seaters are very much could just ad one to your collection.