The bootloader has been added to the Adafruit's fork, so now you can compile it yourself: https://github.com/adafruit/uf2-samdx1/pull/120

Also, the board definition for CircuitPython has been added here: https://github.com/adafruit/circuitpython/pull/2945 — that assumes the correct SCK and MOSI pins, after swapping them.

I ordered the corrected version 1.2 from OSHPark, and it's also available for order here: https://oshpark.com/shared_projects/SXflbZK4 — it's probably not the most price-efficient way to get it, if you panelize it and order from one of the cheap PCB fabs, you could get it really cheap, but with a really long wait.

I even checked that JLCPCB has all the parts (except for the USB socket) in their library, so you could in theory get them to assemble it — except I have no idea how to convert Fritzing's pick-and-place file to one of the formats they require.