Data transfer speeds in USB-C cables have no correlation to charging speeds, as both of these are carried by different lanes in the cable. Therefore, you can buy a USB 2 cable that carries data slowly (at 480 Mbps), but still charges at 100W. You can also buy a data cable that supports USB 3 Gen 2x2 standard and carries data at 20 Gbps but charges only at 60W. Therefore, if it's only charging you're after, you should be completely fine with buying USB 2 cables and checking for the desired voltage and current that they can handle.