Yep. - The selector is a long vertical transfer bar that lies between the firing pins/hammer, with a long skinny leg extending downward to that hole in the RH receiver wall, where the metal takes a 90-degree turn into the hole and the inside of the selector slide/button (which is missing from your gun).
The selectors break at the 90-degree turn, so when yours broke, it most likely fell out somewhere, taking the selector button along with it.
Thanks for confirming that. I want to fix this one so I am starting to make calls to the local shops first. Might be back if that doesn't pan out. Does anyone have a photo of the piece I am looking for or of the gun as it is supposed to look like intact?