2nd Monitor/Memory

Hi

I am currently running FCPX 10.4.4 from my 2012 iMac. But I feel with taking more work on, I need my workspace to be less cluttered on the screen. So I am looking for a reasonable 2nd monitor so I can put my libraries and events on the 2nd screen. Is this possible and are there any recommendations (doesn't have to be 4K).

Also my machine is still purring along with 8GB of memory and I was hoping I could install some more soon. Can you still get memory for the 2012 imac? If so, where's the best place to get it from?

Cheers!