It is really quite convenient, and so far, I have not needed to use external power to do ICSP.
Price is $199.99, 27 in stock, and more expected 2/2/12.
Various retailers on eBay sell the PK3 plus ZIF adapters for $76.95
**broken link removed**
And, that is for a real PK3, not a Chinese knock-off. I got the PK3 from my regular supplier but the sockets from that eBay vendor. His name is Ed, and he is really genuine guy if you need to contact him. I have not received the adapters yet due to a screw-up by PayPal, but in speaking with Ed yesterday, his adapters include jumpers so you can apply external power, if needed.
John