Peter Beck, email@example.com, has many cube spinoffs for sale.
That's where I got the last few I was missing. Jerry Slocum in
Calif also has some items for sale -- I got his address from old
cube-lovers mailings (sent by Peter, I believe). I seem to recall
a few other sources outside the US, but Peter probably can provide
them if there's something Slocum and Peter don't have.