Check this link out for sources of parts.
Where is the best place to search for spare part?
I have not tried to use reproduction parts, but the Uberti S&Ws all have a similar trigger spring and mainspring as used by original S&Ws. In one of David Chicoine's book, he states that the mainspring on Italian copies are altered from the shape of the original, but no reference as to whether they will work or not.