No. Shimano IGHs need the shifters designed to be used for those SPECIFIC internal hubs. There are two available for the 7 speed, the grip shifter, and the rapid fire shifter.
Using a friction shifter is ill advised on the shimano IGHs as slight misalignment will cause significantly increased wear on the parts inside the hub.
Here is (one of many) links for the rapid fire shifter.
Just google search for "Nexus 7S50 7-Speed Rapidfire Shifter" to find more.
EDIT: Here is the grip shifter link.
I have wired up two bikes with nexus 7 speed hubs. One with the grip shifter and one with the thumb shifter/rapidfire shifter. They both work fine.
Here is a different thumb shifter for the nexus 7 made by microshift. Microshift also has grip shifters for it.
EDIT: Here is microshift's official link for all their nexus shifters.
You can't buy them there, but you can find the part numbers to search for.
FINAL_EDIT: I've personally used a microshift grip shifter for my nexus 8 for 3 years now with no hiccups. (Although I would prefer the rapidfire shifter, the 8 speed nexus has no "official" supported 8 speed rapid fire shifter, however the alfine one supposedly works.)
Last edited by corrado33; 03-28-17 at 11:15 AM.