IIRC Northrop did a concept for one. Basic shape like a P-38/Vixen with twin booms.
Each boom was unpressurised with integrated fuel tanks plus a flying boom and hose system, remotely controlled from the cockpit. Carbon composite and contoured for stealth.
The front section with cockpit and engines etc looked like a modified B-2 with a pressurised 2 man crew capsule with individual ejector seats and the copilot with a swing out AAR console.
No size given, but if for penetration with say a 4 ship package, I'd imagine somewhere between sized F-111 and KC-135.