Probably too late, but my ute came with a second Reese hitch welded on at the back and a simple spare holder fabricated that slots in to it.
A bit of a pain if you want to get in via the back of the tray, but does free up space in the tray and avoids putting the weight of the spare up high.
If you're interested I'll take a picture and post when I'm home on R&R.