Technical 1949 Mercury door lock cylinder retainer?

I bought the repop door lock cylinders from Dennis Carpenter, but I cant seem to find any kind of retainer out there anywhere and I wouldn't know what they looked like if I saw one. Any tips on securing these in the door? thanks in advance.

 

My guess is it will be a c-clip like the ones shown below. My past experience with the Dennis Carpenter stuff is that they are too flimsy. I have used large snap rings instead.

 

That's why most Mercs don't have handles or locks!

 

I'm pretty sure it's a cup design that fit's over the cylinder.