Here's an internet/eBay store that sells various types of geta:
eBay Store - REFUSE TO BE USUAL: GETA PLATFORM
Incidentally I'm UK-based and have bought a few things from there, their service has always been really good.
In response to the question of the level of comfort when wearing geta, I'd say no - they're not particularly comfortable at all (especially over long periods of time). They take a bit of getting used to since they are so solid and don't flex at all, unlike most other footwear. However if you've ever worn clogs and found them comfortable then you'll probably have no trouble at all! LOL
Don't let me put you off though, I still love geta and would like to try other types than the pair I've got (mine are closest in shape to the patent ones in the link).