Bear in mind that supersonic capability isn’t of much use to civilians. A high-subsonic trainer is as fast as you’re able to fly.
Yes, the FAA frowns mightily upon civilians flying supersonically outside of narrowly defined limits.
Me? I’d be ecstatic if I owned my own C-172. And if it had an O-360 under the cowl… Woohoo! Supposing I had enough money, my ultimate plane would be a T-38 (which I would fly supersonically only within the rules). I wouldn’t need anything faster or ‘badder’.
Well in that case I’ll take a Harrier, I’ve always wanted to casually rock up to work in a jump-jet.
Anyway, I’m not not American, though I have no idea what rules cover private ownership of ex-military jets in the UK.
IIRC the German nickname for the F-104 was “Erdnagel” (earth-nail).
Relative to weight, yeah… wasn’t the Fokker Triplane rumored to be able to fly straight up?
Short answer to the OP’s question: No you can’t order a military jet directly from Boeing (or any other manufacturer). When the gummint contracts for these, the manufacturer is forbidden from selling to anyone except Uncle Sam. Even foreign military deliveries are handled thru the government’s program office(s); Skipping a lot of details, but from the paperwork/ownership perspective, Boeing, Lockheed, et al are handing off their new jets to the US, who in turn either uses it, or passes it on as they see fit).