Are there available any upgraded power supplies for the EliteDesk 705 G1 SFF?

I see from HP's Partsurfer that there are only three listed power supply options for the HP EliteDesk 705 G1 SFF - all of them provide only 240 watts:

http://partsurfer.hp.com/Search.aspx?type=PROD&SearchText=J4V15EA

The Maintenance & Service guide however lists 240 & 280 watt options on page 230:

http://h10032.www1.hp.com/ctg/Manual/c04497146

Is there anything else more powerful that might be available, and would work as an in-place replacement? I'm interested in something closer to 400-500 watts.

Thank you.