You can source pigtail plugs but they are not cheap. Mine was the same, all factory wiring burnt and previous repairs of trying to solder wire strands onto the terminals, no plug in sight.
When I rewired my windows with relays several years ago I also replaced the factory switch with new, used stud contact terminals similar to what would be inside the plug which I didn't have, and soldered these on and sealed with heatshrink. I then added a 5-wire connector plug below the switch to join to main harness.
Power window switch clips1 by
Aus78Formula, on Flickr