Wait, never pass up an opportunity to get more tools!
Heres a good one at Lowes for under $5 which is only a few $ more then a pack of wet/dry will cost.
8" Mill SpeedFit File
Single-cut for gradual material removal
General purpose file for shaping material or restoring sharp objects.
Tooth pattern, coarseness and length combine to determine filing results.
Uses the SpeedFit handle system for comfort and safety.
Whatever file you get get what's called a "single-cut" file.