C64 PSU specs

I finally got hold of that PSU-less C64 that I mentioned on the list a few weeks ago, followed by a 9VAC PSU to test it with. Other than needing the VIC-II and associated ICs re-seating I've not encountered any problems (I've not tested the 1541 yet though due to lack of a cable). Anyway, I'd like to sort out a better PSU for the machine itself until I can get a genuine one from somewhere - does anyone know what a reasonable max current draw on the 9VAC lines might be? (This is an original 'breadbox' machine) The wall-wart 9VAC PSU that I found for testing is only rated for 400mA, which I suspect might be on the low side; I've seen claims of needing 1A or more, and http://www.hardwarebook.info/C64/128_User_Port only states 100mA max for the user port, suggesting that the machine itself might require quite a lot under certain conditions.