You want a 5mm lead spacing, and a voltage rating of ≥25V for a 9V pedal, and maybe ≥35-50V for an 18V pedal.
Odds are that giant cap is rated for high voltage (say 100s of V) and/or high capacitance (say >1µF) - both factors increase the size.
Note added: I usually get film caps with voltage ratings of 50-100V for caps <200nF. Also watch the thickness of the cap, and see if it fits/matches on the allotted space on the PCB.