I get my cables from:
https://www.primecables.ca/
great quality and very reasonable.
A lot of their cables are from Monoprice in the US - I assume you checked them out.
Lightning to USB-B is an unusual type cable, probably not a lot of demand and thus the price.
However, as a professional musician, I would have thought getting a high quality cable is more important than the price.
But that is obviously your choice.
The only other option I can think of (which would be cheaper) is to use a lightning to USB-A cable and then a USB-A to USB-B adapter, both of which are available at prime cables, and I assume at Monoprice as well.