OK - I pulled the bolt, brought it to a hardware store, found a match and added a lock washer plus a regular washer (it was a mm longer than original) and was good to go. The replacement was stanless steel, tho, no black available, so I will either track down a black or replace the black with a second stainless steel one (I bought 2).
What a relief. Was tough to get it back in without a second hand pushing down on top (the little rubber insulator would push up on the metal piece with the threads) but eventually I got it and the roof is closing tighter than the day I bought it new off the showroom floor.
Black 2000 SE (lovngly maintained)