You can order one straight from Packard Bell's website. I would get the physical measurements on it and see if you could order an aftermarket PSU of same size/fan position and would probably be cheaper.
I assume that when you say "fit the bracket" there is something unique about the overall size and dimensions of the housing of the current PSU.
As best I can determine it is 137mmx128mmx64mm. So....... you'll be looking for something like these as potential replacements
So depending on where you're located you may either try getting on line or on the phone to some local vendors and see what the have in the way of MicroATX or SFX power supplies and then pay particular attention to the physical dimensions, it's likely that anything above the 250 Watt PSU you have currently will get the job done you'll just need to shop for one that will fit, or in the case of the second one I linked to has an adapter bracket.