Couldn't find a good part number here and I think I found one on eBay but not sure if it's the one I'm looking for. Here's the link. Anyone have one for an 01 sierra laying around?

 

your looking for correct?

-99~06 GMC
-99~02 Chevy

i would say that link is right cause the ones for the 03+ Silverado tails have 4 sockets on them not including the part where it plugs into the wiring harness

and the P/N for them (03+ Chevy Harness) is 16531401 and 16531402