I have bought them before off ebay, so just keep checking.
https://www.ebay.com/itm/Maury-Microwave-2740-B-Slide-Screw-Tuner-7-16-0-8-8-0-GHz-2740B/154129531862?hash=item23e2d603d6:g:cxgAAOSwksRff6Ew