Parts for Howard 200?

I think I need an "Oilseal Weston Special W150.100.25 R19" to cure the oil leak on my old Howard 200 rotovator.

Does anyone know if it's still possible to buy such a thing (or two)?

It's a lovely machine but costs a bomb to keep refilling with oil before every use and the leaked oil makes heck of a mess on the shed floor.