Seeing as no one on the planet seems to sell Aprilia Climber spares, I decided to bodge my holed air filter. I just removed the soft sealing lip from the filter, chopped up a Vertemati filter so it was roughly the right size, stuffed it into the airbox so it took up approximately the same area as the old one inside, tucked what was left outside the box under the subframe spars, positioned the soft lip taken off the old filter on top and clamped it all down with the airbox lid.
The hole in the original was made by those stupid spreader things in the airbox lid, the carb had fine grit round it, compression seems to be ok so I'm hoping the bore has escaped unharmed.