Yeah there is Bob. It is available through dealers (such as myself) who have accounts with Australian Carlton distributor Jakmax (amongst hundreds of other things they sell). I'm could be wrong but I'm sure it would be available in the US via someone although probably not marketed under Jakmax?
Jakmax part # is ST0621 (Stihl part # 1127 020 1216).
Details from their catalogue are:
Dia 49mm. Fits models MS390 and 039. Includes piston, pin, rings, and clips.
It is a new item that only came out in their new catalogue this month.
If desperate I can get one to you but with our current exchange rate and the price of postage I think you'd probably choke, unless about USD$220 sounds OK Excellent value in Australia!