You just missed one on Ebay!
There are a lot of similar folding caravans though, so if these particular ones are proving to be hard to find, you could always go for something similar. Does it have to be that exact model?
I had the same problem when I decided I wanted a small Kip caravan. These are also very rare... one came along and I bought it, then threw a lot of money at it, did it up and stopped it leaking.. long story! But I thought I was going to have to drive to Holland and buy one and bring it home as there are very few in the country. The newer Kips are there a-plenty, but not the little classic ones.
Have a look at the Esterelle and Gobur folding caravans, they are so similar that I can't tell the difference.