I've found a couple of R7s and R8s in the wild. These are off the top of my head:
Psychic Detective (PSX - R8 - complete, $5.99 at EB)
Streets of Rage 2 (SMS - R8 - boxed, $10 at PC5)
Flintstones: SADP (NES- R7 - loose, $4.99 at GS)
Namco Ms. Pac-Man (NES - R7 - boxed, $14.99 at GS)
Namco Pac-Man (NES - R7 - complete, $12.99 at GS)
I may have one or two more, but not sure at the moment. I've also found a ton of great R5 and R6 stuff for NES in the wild (Bubble Bobble 2, Bonk's Adventure, Cowboy Kid boxed, all the Dragon Warriors a few complete, Jungle Book complete, Little Samson, Mario's Time Machine, Panic Restuarant, Race America, Snow Brothers, etc.).