Searching 80+ ATX PSUs here, I find quite a few PSUs that look good for low-power applications but they all appear to be OEM parts for HP, Dell, and Lenovo. The worst part is searching for the part numbers on the OEM Web sites turns up nothing. For example, Lenovo has a 180W PSU rated at over 91%...
Low-Power ATX PSU's - Where to get
Low-Power ATX PSU's - Where to get