I would suggest using something like Cryptomator:
Note that this won't encrypt an existing folder. It first creates one, which you can use to place sensitive files. However, you can drag and drop your entire folder inside this newly encrypted folder.
One important thing to remember is that you should not interact with this folder until you have unencrypted it through Cryptomator, otherwise your files would be very much readable.
Another option is to create an archive (.zip file) that is password-protected. Again, this won't protect your actual folder as it is, you'll have to delete it afterwards, and then restore from the archive.
NOTE: Password-protected is not the same as encrypted. This archive can still be access by someone with enough experience. Since you're taking this to a repair shop I would argue this isn't a good enough protection, but this may still be useful to deter an attacker in other situations.