J.C. Higgins trigger group?

[Boomer454]

I was out at at the farm today and dad asked me if I could find out how to fix his old J.C. Higgins shot gun.

It's a model 20 and the 2 little ears on the front of the trigger group are broken off. It seems to need these to stay locked up. You have to hold up on it, or hold the forend ahead to keep it closed under recoil.

Obviously it hasn't been shot in years because of this, but he'd like to get it working again.
Does anyone know of a fix? Or where a trigger group housing could be sourced from?

 

[Rugdoc]

J.C. Higgins Model 20 is a High Standard according my my reference book, but it doesn't specify the model number.

 

[gunrunner100]

Is it a pump or semi? I have a semi-auto parts gun.