Is there a tool to real-time encrypt folders?

I'm looking for a veracrypt/truecrypt equivalent but at the folder-level and dynamic sizing

Something like a tool which could encrypt folders in real-time and then be able to lock it up. Truecrypt expects me to provide a size for it, I'd like something more dynamically sizeable based on the files I store in it.

Even just a tool that encrypts files written into it and converts them to other files works with me