Thanks to Robbie for keeping this chain going, albeit off line.  Yes,
these "zitheroids" (Great term!) are fascinating; yes, they are all over
eBay and typically go for $75 to $125; and yes, I have acquired "a few"
of them.

As I stated earlier, they are of interest as "semi-automated"
instruments, though to be honest, considerable practice is needed to
sound good.  I once read that door-to-door salesmen practiced hard to
learn to play one demonstration piece really well on the the "Hawaiian
Tremoloa".  They'd impress the customers with that music, but after the
sale, the customer would find that you had to practice and work at it
to play as well.  Just like a...  well, a musical instrument!

I think my roller zither is called a "Paramount Harp."  I've seen them
on eBay with various maker's or agent's names.  Of course eBay sellers
tend to use names like harp, zither, and Autoharp willy-nilly.  Makes
searching for them more of a job, but the work is repaid in humor
sometimes.  I don't think eBay will be opening a zitheroid category
very soon.  :-) 

I'd love to watch someone really play the true Austrian zither -- that
instrument must take years of practice.

Mike Knudsen