Indeed they did go the cheap route with the wooden cap. Before about 1990 they all had brass bases. It is strange that the worthless plastic part does not just fall out of the wooden part. Perhaps you could pull the wood top off the plastic part when the plastic part was screwed into the boiler part? If you could get the top off the junk plastic, you could probably reattach the two pieces with good epoxy resin. If you should do that, you would need to be sure to allow plenty of time for the resin to cure after using it. Asnother alternative is to find an old discarded brass based plastic topped cap and throw away the junk plastic. As mentioned earlier, is also not too hard to make a brass cap base, but you need some machine shop equipment to do that.