Fisher manufactured all the slides and most of the coverslips we have. As I mentioned, we had them on hand, and haven't had to order them for some time, due to having several boxes of the ones we need. So, all I can suggest is contact your ThermoFisherScientific rep for modern-day equivalents. The exception is the 48x65 mm coverslips, which were obtained from Becton Dickinson Labware, their reorder number was 3335. These we obtained more recently, but it was probably a few years ago. Anything has to be better than applying four coverslips on one slide, as you mentioned.
Hope this helps,
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