US $21.42 15%OFF | ULT-Best USB 3.0 Front Panel Bracket Motherboard 20 pin to USB 3.0 + Type-C Port HUB Adapter Cable for 2.5" Floppy Drive
[URL unfurl="true"]https://s.click.aliexpress.com/e/tqDTzyJW[/URL]
US $12.96 20%OFF | LBSC USB Type-C floppy drive front panel USB3.0 AF+C female computer expansion
[URL unfurl="true"]https://s.click.aliexpress.com/e/ozyQqnzO[/URL]
[$570 for 30 = $19each] US $570.00 5%OFF | (30 pieces/lot) USB 3.0 Type-A & USB 3.1 Type-C USB-C Dual Port to Motherboard 20Pin Front Panel for 3.5" Inch Floppy Bay
[URL unfurl="true"]https://s.click.aliexpress.com/e/N2Y8x0eG[/URL]
*[Cheapest option I could find without cable] US $12.88 20%OFF | LBSC USB Type-C floppy drive front panel USB3.0 AF+C female computer expansion
[URL unfurl="true"]https://s.click.aliexpress.com/e/ePg2jCtK[/URL]
*[Cheapest option I could find with cable] US $16.88 | Great-Q USB 3.0 Type-A & USB 3.1 Type-C USB-C Dual Port to Motherboard 20Pin Front Panel for 3.5" Floppy Bay
[URL unfurl="true"]https://s.click.aliexpress.com/e/ntKzBcmc[/URL]
* Just because it's the cheapest individual doesn't mean it would be the best price bulk
Maybe you can get bulk discount on one/some of these?
If you buy a bunch they may even be able to sell them w/o the metal chassis (save on cost and shipping), just a thought. 
Edit: some do not come with a internal usb3.0 cable... But you could order those seperatly potentially (either stateside or overseas). Also I cannot attest to the quality of these, but I thought I'd share because the PCB is similar to ones you've used previously.
