I did see a couple of working but untested ones offered for sale on eBay a few months back that went for around £25 - if I remember correctly, I was nearly tempted to have a bid myself just to have a look at them.
I could see them becoming really collectible in the future.
Do you change the water instead of changing the battery? Do yours work? Any pictures?
I remember seeing a 'potato clock' around the same time (early 80s) very funky!!! You would look daft with a potato stuck to your wrist though.