Digikey is nice because you can filter for things like size.
Select the capacitor family, in this case aluminum to start, it is the only family to offer cap's of that value
Select cap value
Select mounting method.
In this case you will find that all are round - so it comes down to selecting a size you can live with, and a voltage range that is higher than you expect to have applied (by 25% to 50% minumum, this is known as derating the part).