I'd probably opt for a M-31X level.
9 speed will be just a bit narrower and more prone to rub on the wider 7 speed chain.
Even a Tourney level will work fine when used in "conventional" configurations.
This is my 22-32-36 with a Tourney on my 9 speed Globe. You can see the gawdawful gap.
It does need a bit of help going to the largest ring, but considering the largest ring should have 6-8 more teeth.....