Jason,
I tried a Google on this very thing. Came up with some intersting stuff on a US squadron that came back from the ETO at the end of the war with 262's. In fact I know there is a decal sheet out there, just can not remember who put it out. Sadly I would not consider this group to qualify.
The best suggestion I could make is to look at individual nations air force histories. Many of them should mention when they converted to jets. Many of the Third World countries may be difficult to find histories due to volatility in thier governments, but it may be a good bet that it was probably a MiG 15 or 17. I know Argentina was one of the first to receive A4's. May be worth a look see to see if it was thier first jet...
Speaking of 262's...what was the post war Luftwaffe's first jet...may be a Sabre perhaps....that would be interesting.
The whole idea is to do a "first"...262's and P80 of course, but the first to serve with an Air Force, or even the "first" domestic jet produced...