Rimfire Technologies and DIP are two separate companies. The trigger guard is available at DIP, it's not longer available through Rimfire Technologies. The machine work from DIP is excellent. It's not (never was) an assembly though, it's a stripped aluminum trigger guard.
http://www.diproductsinc.com/Default.aspx
Go here to buy a new production metal Trigger Guard Assembly
https://www.rimfiretechnologies.com/ProductDetails.asp?ProductCode=15001
Old Answer,
You should be able to use the stainless steel assembly from the Model 60SS. However, replacing the trigger assembly will probably cost as much as the gun is worth.
At a good gunsmith's shop. Maybe Numrich's Gun Parts (search gunpartscorp) For the complete trigger guard assembly, including trigger, safety, springs, pins etc., you can get it from Numrich, Midway USA, Brownells or direct from Marlin. If it's just the trigger or other individual trigger guard parts you need, you'll have to get those from Numrich for a different model Marlin.
gunpartscorp website.
No.
try looking under the trigger guard. That's where I found my Model 99 M1 Cal-22LRserial number
Model variation
If your Mdl 42 is a bolt action 22 rifle, it is a Marlin Mdl 80. There were 5 different trigger guards used at different times. Go to the wbsite for gunpartscorp, select M, then Marlin-Glenfield. Model 80, scroll down to part 78. Some of them are in stock.
Remove the trigger assembly. It should only be 3 screws. The serial number is located on the bottom of that plate. (At least it is on my model 99 m1)
The serial number is located about 3 1/2 inches forward of the center of the trigger guard on the left side of the rifle.
well marlin introduced the marlin model 43 in 1922 so mabey when u figure out what you really have you could try another question My Marlin Model 43 12 gauge pump (Model number is stamped underneath, in front of the trigger guard) has Pat. 1908 on the barrel. There is also a patent date of 1922. Looks like Marlin did produce the Model 43 earlier than the 1922 date you have.
I have a marlin model 60 with a gold trigger..the price difference is not by much if any at all..they both cost the same. some gun shops will charge more, but most usually don't and charge the same. A model 60 with etching and wood work can sell for more than one with just a gold trigger.
Might have been replaced.
Smith and Wesson Model No. 2