Not much to go on, but there's really not much difference in shopping for a 7 vs 6 string. Some of the same named pickups will sound about the same more or less as their 6 string counterpart.
Look at the EQ curves, DCResistance and output and go with something that has the power and EQ curve you're looking for.
I much prefer the 6 string version of the Black Winter over the seven string version. They’re quite different sounding. 6 string version is amazing, but I found the seven string version overly harsh and fizzy.