There is not a readily available alternative for them. Luckily, unless they have been abused i.e. sandblasted, or gouged then it's not a problem. The PD model carbs use a rubber tipped valve also as opposed to a metal tip, so it can give you some degree of forgiveness compared to a metal tip which will not conform at all. You can attempt to polish the seats to remove any micro pitting. With new float valves you should be ok.
