You’re not out of luck at all! Using 16V capacitors is perfectly fine for most pedal builds — especially since nearly all guitar pedals, including all of ours, are designed to run on 9V power.
The only time 16V caps would be a concern is if you were planning to run the pedal at 18V, which some builders do to increase headroom. But if you’re sticking with the standard 9V supply, those 16V caps will work just as intended.