Seems to me that the choices are either the Pocketop and its er, “clone”, the Micro Innovations Universal keyboard; or the Belkin Universal keyboard and its apparent “clone”, the Snapntype PDA keyboard. (Oh, the perils of manufacturing nifty small gadgets in China!)
It seems that these may be found for as low as ten US dollars from time to time (of course, shipping will typically be $20 to NZ). The Pocketop is smaller, and arguably cooler, but is missing the number keys (these are accessed through a modifier key). The Belkin is a little larger but has a more standard layout.
There are a couple of other options (such as the Palm Wireless Keyboard and the Saitek Universal IR Keyboard, but these either lack drivers for both devices or simply could not physically accommodate the phone.
It’s all a bit academic really, as I’m a bit gunshy about eBay deals that just seem too good. I came close to being burned once before by an apparently OK seller who suddenly went bad on the auctions just preceding mine. Luckily I had sent no money away before the warning signs appeared… but still, I’m more cautious now.
And I’m really going to have to write some more interesting stuff here. This is getting increasingly geeky and boring.