The portable desktop range somewhat died before the high end 486 / Pentium era, so I'm not sure if you'll get one quite that high spec.
Compaq Portable 486DX2-50 would be my recommendation if you don't mind some weight. Colour LCD built in, mains operated, 2 or 3 expansion slots (can't remember) - in mine I have a network card and generic sound blaster clone - plays Doom great
I'm hesitant to sell, not because I"m a tight ass, but more because my unit isn't perfect - the keyboard cable is frayed, it's missing the disk drive button, and the screen is losing contrast (it gets better after 10-15 minutes). But if you see a good one on trademe, definately snap it up. Their $10-12,000 price tag in NZ made them quite rare to see.
Another option is the Toshiba T series - the portable desktop - for a while I was using mine as a bridge for copying files off the network through a serial cable to an XT. The T5200 is a good model, 386DX-20 with 2MB RAM standard (handy if you get one with a memory expansion though). The display is orange plasma, but there is an external VGA connector if you need it. I run a sound card in the 16 bit slot, and a network card in the 8bit slot (16 bit card configured for 8 bit mode). They are starting to get a little fiddly with age however, and they are very picky with what hard drive is used (must be a Conner CP IDE).
All are mains only powered, single connector. The compaq is huge and heavy, the Toshiba's are a little lighter but much easier to carry.
I haven't seen any other ISA laptops turn up on trademe, just more Toshiba's like the T3100e etc.
Compaq Portable:
Toshiba T series:
http://www.toshiba-europe.com/computers ... index.shtmEdit: If you can give up the ISA requirement, I have a range of tested Pentium laptops, mostly Toshiba, some with battery and some mains only. I also have a few Pentium desktops. I go to TrashPalace occasionally and grab an untested laptop for $50 and bring it home to fix, however most of the time the Toshiba's just boot up with no faults.
Edit2: the earlier Toshiba T series, e.g. T3100E or T3200 may not have VGA, best to check before hand, T3200SX and T5200 are definately VGA though.