At the 2012 Orlando IPMS Nationals, Model Rectifier Corporation made a special decal sheet of multi-nationals roundel insignia available for giveaway at their show booth. I was lucky enough to receive one of those sheets from the IPMS Reviewer Corps.
This sheet contains national markings for USA modern aircraft (color stars & bars), Japan, Australia, Russia, Soviet Union, Germany, China, Italy and Canada, in various sizes and scales from relatively large to tiny.
I built an old Starfix 1/72 T-38 for my father’s career aircraft collection, and the decals were unusable. I found some USAF lettering in my spares box, but used the stars and bars from this sheet. They went down smoothly, and with a touch of Solvaset, nestled down into the re-scribed surface detailing I applied. They made a mediocre kit look good. I will keep this sheet on hand to use in similar situations.