I took a look and also could not locate anything that was USB-C male to USB-A female that was rated for 10 gbps.
If you value the 10 gbps connection speed above all else, then you may very well be better off shifting your focus and parting with some additional money. Replace the thumb drives with native USB-C 3.2 Gen 2 10 gbps drives, and look for replacement cables specifically between the connectors on your external hard drives and the USB-C on your computer.
One thing to keep in mind is that if the external drives are indeed hard drives and not SSDs, then the SATA bus on the drive itself is going to be limited to 6 gbps. A 10 gbps USB connection to the drive may not buy you much, if any, real world improvement.