How to copy from the current user?

When we are registering a user for an event, we need to clone their user field data for audit purposes. It seems to be okay if I manually select the user, but I don't want the user to have to do that; it should just use the "currently logged in user." Is there some way to do that?

It would save so much time to have this module do it instead of my having to reinvent the wheel.