I personally have moved on to widescreen (16:10 1680x1050 being my favorite) due to the ability to split the screen in a editor|browser or editor|pdf configuration (or two-pane editing).
They weren't hard to come by about half a year ago when I bought one. It came without a battery or AC adapter. I paid $256.
Edit - I just checked eBay and searched for "T61p". I found:
* A 4:3 T61p with an incorrect description for $500. That seems high.
* A 4:3 T61p missing its palmrest and other parts, auction only.
* A T61p in a T60 chassis with a QXGA panel, SSD and other upgrades for $1300. That sounds high unless you've tried to find a QXGA panel; they're over $400.
I miss 4:3 on X60s/X61s because it was so much smaller. I like how widescreen makes keyboard bigger though; I just wish for more portable laptop, more like Air but still user-configurable.
I pull out my old T42 from time to time and it's so relaxing to code on such a screen ratio.