Watch online auctions. Beat up boxes with ammo sometimes goes for a reasonable price. I think you can find full boxes for $50, which sounds like too much, but how often are you really going to shoot those old tip-ups.
Before Navy Arms imported 32rf, I shot lots of original 32 ammo. Never had one misfire on ammo that was up to 100 years old. I was fortunate to have bought a case of both long and short 32rf and am set for awhile longer.
Last resort would be to buy those reloadable cases that use a 22 blank as primer. I think Dixie Gunworks still has them.