WinAce and PowerZip offer password protection but, They would have to pay per password for each file.

Way back when, there was a site that did this with powerzip, membership included a password to unlock zipped movie files. There is a trial version of PowerZip you can download then you have to purchase PowerZip to open the files that they have bought after the trial expires. Double profit if PowerZip has an affiliate program.
:nobody: