I checked with epwi and itm units in all sizes except std have been on back order since march. And they don't think they are coming in anytime soon. My source for sealed power units said check eBay and parts stores sometimes you can find them sitting in a warehouse.
I think your best bet is to find another head. I think your valves and springs will interchange. So you'll just be in for guides seats seals and machine work.
Bummer man good luck!