No, you can’t buy the seal. Rule of thumb is WMA type 1604473 big bearings have an alloy pulley, machines with the 30mm shaft and 1604600 bearings have a plastic pulley.
Most of the WF range 1400rpm and under have 30mm bearings they usually have a whiteish back half the ones with 35mm bearings are 1500 and 1600rpm and the back half is blueish, as for the alloy pulleys they were only fitted to the early WMA’S they fitted plastic pulleys to all the differant spin speed drums since cheers Jj