I don't know much about the Remington 742 to be honest.
is a company that we buy a lot of Remington drop ins from. They make a very good trigger. I don't know if they have your specific model I am afraid.
I am afraid I don't know of anyone out there that is making a drop in if the folks at Rifle Basix aren't.
As a way of consulation, any quality gunsmith can do a decent trigger job on the stock trigger and improve it for you.
Best of luck -