Is it a circular spring on the shaft of the pedal?
If it is, well your not going to like this, two issues,
#1 You can't replace that spring properly without cutting the pedal out of the step, hence the reason they don't show a replaceable P/N.
#2 The part numbers for a springs that might work are discontinued, but you can try.
P/N 35219-17530
P/N 37150-17530
Better and easier option: Weld a tab on the pedal shaft and use a standard pull type spring to fix it.