Hello Paul,
I *think* I may have briefly seen the Tropical Kingbird today. I saw the bird sitting on a wire just as I pulled into the entrance and parked in front of the sign for South Platte Park. It was a couple of wires below below several European Starlings. It was marginally larger than them, and had a long bill. It flew downward before I could get a photo. I stayed around the area for about 20 minutes and it didn't return. I checked all around the RPM building, and down the road just to the curve (where there are lots of Lesser Goldfinches).
I can't be sure if I saw it, but if it's not too out of your way to Pueblo you could try to see it.