I found a solution for the broken Glove Box Door Latch Striker on my 1984 Riviera. I suspect that this part is the same on all 1979 to 1985, but I am not sure.
When the plastic portion of this part broke, I had modified it and got it to work for a while, but it eventually broke again. I found a part on Ebay that looked like the same plastic part with a different metal portion of the striker assembly. I bought one and just got it.
Here is the link:
GM# 10054054 BUICK GLOVE BOX DOOR STRIKER 1982-1996 NOS : eBay Motors (item 200434164475 end time Mar-01-10 15:38:47 PST)
The plastic portion of the assembly is the same, I simply swapped the metal portion of the striker assembly from my old assembly to the plastic portion of the new assembly and it is as good as new. He has two more available.
I have not checked, but since this part number, 10054054, apparently is used all the way to 1996, perhaps some GM dealers might still have some available after these on Ebay are gone.