Same place you found(Diversified). Except I got mine on ebay through their ebay store. When I bought mine they weren't being advertised like they are now in the magazines. I guess they were testing the waters to see if they would sell. Now they are everywhere it seems. I have seen these heads go for a few hundred more though. I paid $724 to my door last July.
Damn $724 to the door is really good. You think I can have Summit price match them because isn't shipping only like $9 for Summit now. I don't know if this would apply to larger items like heads. It's worth a shot.
Summit is real good about price matching. They don't have "shipping charges". They have an $8 handling fee. As long as it is not an oversized item then they usually don't charge for shipping.
I was looking on Summit's site and I found the heads but there was no price and no shipping date I don't think. So I don't know if the price matching is possible.