I just replaced one of the blown up RIFA caps in my Apple II+’s PSU. Most places will point you towards vintage Apple sites selling these caps for a markup. I purchased my replacement caps from DigiKey, you can find them at

https://www.digikey.com/en/products/detail/kemet/PME271M610MR30/3459439

or under the part number PME271M610MR30. They’re avaliable at Mouser too, but they are significantly backordered.