I'm looking at modding y beige powermac G3 and I need a small power supply wih dimensions no bigger than 16cm(w) x 18cm(L) x 8.5cm(H) and preferably not much more than 150w of power.
I used shuttle PSU's in my Black PowerMac mod (in the contest this year), and they're pretty small considering their power output. The dimensions are 82mm x 43mm x 190 mm. I realize that that's a bit over on your length requirement, but it's much smaller in the other two dimensions.