They're still listed in EPC. There are multiple part numbers: 000939010077, 000939010047, 000939010123, 000939008130 and 000939010126, which assume refer to different lengths, or maybe a part that's often superseded. The exhaust nuts are 0009903150.

I can't find these part numbers at any online site, so I assume they are generic parts. The dealer should be able to help. You may be able to find an off the shelf stud that would work:

https://www.oreillyauto.com/shop/b/performance-16477/exhaust-16555/exhaust-manifold-header-bolts---studs-17878/1ae38bae6636