If you can get some Roy stuff. Thats the ultimate, but he's not still making jeans
Well the ultimate in MiUSA denim is probably Bowery Blue but it's so insanely inside baseball denim/sewing nerdery that it isn't relevant let alone worth it for most people.
Background (I imagine you know this, but sharing since TFL is probably the audience for this stuff): The owner of Bowery Blue is a sewing machine expert and collector from Japan, who lives in New York. His interest is really in sewing machines and sewing techniques more than denim per se.
He makes a few different models of jeans with exactly period accurate techniques– to the obsessive extent that there are two similar pairs, one of which costs a few times more– because the mid-19th century machine used to sew it takes several times longer to use in working time. There's actually a little warning by that model saying only to order it if you specifically want that. Clearly someone who knows his audience.
I'm genuinely tempted to place an order with him in person before I move to California.