Ahhh, too late for suggestions, then. Still, I suspect you've discovered that a press fit is easily enough to hold your pinion in place. I was going to suggest you make it easier on yourself and get the pinion nice and hot with a torch before you press it, but you've apparently managed.
Other option is hunting up the gear, as you've said. The tricky part is determining whether it's inch or metric, not finding the DP or a supplier. Suppliers are easy:
SDP-SI or
WM Berg