If you've never ridden a rigid bike - do yourself a favor and try some struts for a couple weeks first - that way, when you figure out how bad the ride is, you are able to easily change back.
They're out there....just do a google search for "rubber mount Sportster hardtail" and several companies come right up....including Elswick Cycles, who suck. Don't use them.
I realize this as well, but I don't think that Hammer in Hand makes one.