Searching for LFB1-LNRZE

I need to check if a vendor is a 'head office vendor' and that would require a select on table LFB1 to check field LNRZE to see if that vendor is there. This field is not indexed, so a sequential read of the entire table would be performed (not a good idea!). Does anyone have a suggestion? Should I have our basis people put an index on that field?