Dredging this back up to share what I have learned (and what I haven't) about this Wilton mill.
It took a couple tries, but I eventually got a response from JPW Industries. They confirmed that my mill is a VS203. They even provided a manual. But, they are non-committal on parts availability. They gave me a phone number and advised to ask by part number with no promise all parts will be available.
As I said earlier, this mill appears to be identical to the Jet JTM-4VS. So I took a look at the on-line parts diagram for the Jet machine. It is literally identical to the Wilton manual diagram. Well, the actual part numbers are different, but the diagrams themselves are the same down to the index numbers. So, armed with this, I went back to JPW. They stood their ground, telling me that a "few parts" were the same. I can't tell if this is all CYA or what.
H&W don't have any info on the VS203, but they do carry a head rebuild kit for the JTM. My thought is to give it a try. Anyone else have any luck with parts interoperability between these machines?