Terry Tussey does some really good work on Vaqueros and various other models of revolvers.
While I have not used his services in the past, I would point out that pretty much everybody who knows who he is would vouch for him.
I don't know if he does work on 1890-s, but, it couldn't hurt to ask. The price-guide on his web-site states that trigger work on a single action Colt clone goes for $170. Couldn't be that far off...
By the way, he would be reached in Carson City, Nevada.
If that seems like too much to go through for your beloved wheelguns, do what everyone else does. Try to make friends with your favorite local firearms dealers and see who they go to.
My two cents, you can take it or chuck it into the cuspidor...