I've had a lot of fun looking for Pyuuta things on Yahoo! Japan lately. Unfortunately, I missed the boxed Pyuuta Jr. Tape Interface (yes, they really do exist--it is the second one I've seen for sale this year). I also saw an odd thing with a regular Pyuuta--it had a BASIC-1 overlay for the keyboard. It didn't have a BASIC-1 module though--just the overlay. From that, it makes me think that it was somehow possible to use the BASIC-1 with a regular Pyuuta (maybe with the cartridge expander box?).
I did win some of the items I was in pursuit of though--a pair of tapes, which brings me to a grand total of three Pyuuta tapes (the one I have is UFO).
Tomy also apparently sold two different tape drives for the Pyuuta in Japan. The seller of the cassette interface also sold a cassette drive, but the bidding for that one went really high fast, so I don't think many of that variety were sold. It may have just been the fact that it was in a crisp original box too. . .
There are a lot of Japanese release cartridges up for sale right now, some for very realonable prices. There are more Pyuuta things on sale there over the last couple of weeks than I've seen in years!