A friend had the same problem.
His Tiny machine is circa February 2002 and power supply went down.
"Non-Standard" as quoted by the repairer probably means that it is an AT case not ATX.
The PSU fitted to my friend's PC was a 150w AT and it took a little bit of metalworking and fiddling to fit a 300w ATX , but it went in and PC is fine.
I got the PSU from savastore.co.uk for £15.20 incl delivery.