Top to bottom:
taylor stitch overshirt
taylor supply belt
dayton service boots
Bonus: brown oiled dayton boots with new mini-lug sole.
Maybe tucked is formal enough and the blazer is too much but that doesn't work the other way around as you are suggesting. An untucked shirt with a blazer is always going to look sloppy, trashy, etc. If you're trying to strike a balance, there are better ways than this. This doesn't work.