I don't think a desert island one exists at that price point, in fact can you even get a ribbon mic at all at that price?
If I was going to a desert island with a bunch of mic geeks, I'd spend the $250 on food and then wait for someone to be hungry and thirsty enough to trade me a Royer R121 or at least an R101 for a couple of sandwiches and a can of coke
Tbf, although not my "desert island" ribbon, the Apex 205 with even the basic blast filter mod is outstanding for £69 (what's that, about $100 ish???).
I'm also surprised not to see any mention of anything Cascade yet....
And the Avantone looks ace, but i am a sucker for most things Avantone
I don't know that sub $250 and desert island go together for me! If I could choose any mic it would be a CLOUD JRS-34 or possibly their new 44 coming out this month. Haven't heard it yet but my buddy says it sounds amazing!