What they said, go for the highest voltage rating you can get, just provides additional overhead.
If for some reason online is a problem, appliance repair places (washing machines, dryers, dishwashers, etc.) and pump
sales/repair (swimming pool, small farm systems, water
well, etc.) places will likely have a bucket full of suitable capacitors. In a pinch the exact rating is not critical, you could probably go from 30 uF to 40uF and still be in acceptable voltage range.