For folks in the UK, Tottenham Court Road (Central London) is generally the place to go for hard-to-find electronics gear, but even then the economic downturn has been evident in a reduction in the amount of bleeding-edge gear available there.
You can sometimes get a good deal there, but it's not for the faint of heart. They're a bunch of sharks and they can smell weakness or uncertainty in the punters within just a second or two after they've walked into the shop. You need to know exactly what you want, and the sellers sometimes try to trip you up by asking you "how much do you wanna pay?", so you need to know exactly how low / high you are willing to pay and you need to have cash, not cards. Oh, and you need to dress in nothing fancier than jeans and a T-shirt, with no jewellery or watch, and no fancy shoes/trainers. If they sniff that you may have more cash than you're letting on, you'll never get their best price.
I recall paying about £230 for a D-777 Discman when everyone was retailing them for £299 - £320 (this was when they were 'just off the ship', very rare in the UK, and in high demand from head-fi geeks), but I had to go in the shop with such confidence that they ended up whimpering at the price I got them to sell it for.
I'm not saying that to brag - I'm simply mentioning it to describe how merciless (but always polite) you need to be with them. Not so much merciless with words, but in certitude and self-confidence.
I no longer live in London but if anyone reading this thread is considering buying a ZX1 in the UK, please consider visiting Tottenham Court Road if you have the necessary self-confidence, described above, and can't find a decent deal online. It's a buyer's market at the moment.