I highly doubt that your hammer is actually stainless because, to my knowledge, stainless internal parts were discontinued with the introduction of the 66-1 due to galling issues. More likely, your hammer and trigger are flash hard chromed. Gun Parts Corp. has the part you need though, as Mike Irwin pointed out, it may not return a DAO gun to DA/SA.
http://www.gunpartscorp.com/Products/313990.htm