1. Remove all visible links on the website that point to the listings.
2. (Optional) Change the URL/Folder of the listings section if you don't want existing bookmarks to work.
3. Send out an email out to all existing members, including an explanation and the (now hidden) link/URL pointing to the listings section. And ask that they not share the URL with others...
NOTE: If you change the URL for the listings section, you might modify the pages served up from any existing inbound links or bookmarks that still point to the "old" listing section too, those pages should display a notice about the new change(s), or something more appropriate.
Best of all - its QUICK! No one has to mess with registrations and you could have the whole thing done in a couple hours or less, probably.
BTW - I do accept Paypal donations -
