I've seen these in Japan a few times, and they are indeed the lens from a Konica Wai Wai remounted. In Japan they were a bit cheaper than 250 Euros, but sill pretty expensive. The conversion is quite professionally done though and the lens is actually surprisingly good, it's also very small.
The Wai Wai can be had off of ebay for a tenner or so and the conversion is farily easy to do yourself - there's a few websites out there which detail it. I don't have any links on me as my mac is back in England but a bit of googling should turn them up.