If you would like to add these two rarities to your own Stylophone collection, try the UK version of eBay. It is not unusual to see treble Stylophones listed there, priced around the equivalent of $15 to $30 USD. I've seen several treble Stylophones listed on the US version of eBay as well.
The bass model seems to be quite rare, so it may take some patience and luck to find one. I had an automatic search set up on eBay for a couple of years before I was able to buy one from a seller in France. As I recall, the purchase price was around $15 USD, but the shipping cost was around $30. When the instrument arrived, I fired it up and it worked for only about 30-seconds. I took it to a local amplifier and keyboard repair shop, along with a copy of the circuit schematic I found online. They were able to replace a few failed components on the circuit board and have it sounding almost good-as-new. The repair job cost me around $70, but should have cost more. The technician gave me a discount because he found the project amusing. So, my $15 bass Stylophone was not such a bargain after all.
I find the treble version of the Stylophone to work and sound as expected. The bass model doesn't seem to be quite in-tune in the lower few notes. I don't know if this is due to the original design, the age of the instrument, or the repair job.
The bass and treble Stylophones are certainly not essential for any musical application. A standard model can be pitched up or down with a computer DAW or an effects pedal for very similar results, but I find it fun to have these peculiar variants in my already peculiar collection of vintage Stylophones.