Need Some Dis-continued Jam Nuts

[Hants]

I'm looking for a 7/8'', 18 Thread, RH and LH nuts for tie rod ends on a 1987 Chev 1/2 Ton 4x4. After you screw the tie rod ends into either side of the long sleeve, the nuts are used to snug up to the sleeve to lock the tie rods in. I've been looking everywhere and the GM dealership says they are dis-continued. I've also tried other 7/8 nuts both coarse and fine but they need to be 18 thread. Can anyone tell me where to get these nuts? Thanks.