Bring on the Faroe Islands! ...wait, no, they've got matches 11/14 and 11/17. Actually, everyone in Europe either plays Sat the 14th / Tues the 17th, or Sun the 15th / Weds the 18th (Wales is the latter; frankly we're lucky they agreed to 11/12). We need a team from outside Europe who'd be willing to play us in Europe.
CONMEBOL is having WCQs on 11/12 and 11/17. AFC is having WCQs on 11/14 and 11/19. New Zealand probably couldn't get the band together there (their roster is 4x MLS, 7x AUS A-League, 10x UEFA), and at rank #121 I doubt we'd learn much from playing them.
CAF is the only real possibility: They're having two AfCoN Qualifier matches on 11/9 and 11/17, and most Pot 1 teams would be good matchups for us. As we know, African FAs are always in need of cash. They'd be somewhat crazy to agree to a match with us on 11/15, but if they're in a strong position in their group and playing a minnow on the 11/17 that they can rotate heavily against, I wouldn't say it's impossible, especially if we charter them some flights or something. But man, we'd be calling in some favors, or playing on 11/14 on 1 day rest. Contenders in my mind:
(1) Ghana - Rank #50, currently 1st / 6 pts in their group, plays 11/9 vs Sudan (3rd, 3pts), 11/17 @Sudan; nearly everyone is UEFA-based, and we have a legit rivalry with them so we can promote the hell out of the match
(2) Morocco - Rank #47, currently 1st / 4 pts in their group, plays 11/9 vs CAR (3rd, 3 pts), 11/17 @Burundi (4th, 0 pts, -5, Rank #134). Has a hell of a roster, and the US playing in Morocco on 11/15 isn't absurd geographically.
(3) Cameroon - Rank #51, is the host of the 2021 AfCoN and as a result is basically just playing friendlies out there, 11/9 vs Mozambique, 11/17 @Mozambique. One of the most decorated African teams. Big commute, but no performance pressure.
(4) Senegal - Rank #22, the #1 team in Africa; currently 1st / 6 pts in group, plays 11/9 vs Guinea-Bissau (3rd, 3pts, #118), 11/17 @ Guinea-Bissau. Star-studded lineup. Would televise great, could maybe play in France
(5) Nigeria - Rank #45, currently 1st / 6 pts in group, plays 11/9 vs Sierra Leone (4th, 1 pt, #115), 11/17 @ Sierra Leone
Or, my preferred idea, find a coach to assemble a "Team Ronin" of UK-nationality players who aren't good enough to play for their national teams but are in the EPL or thereabouts, and who'd relish a chance to compete in an international friendly on the UEFA off-day (Mon 11/16). You only need 15-16 of them or so.