Corning adapter and cable available on Amazon, $215 for 18 ft. Max speed: Thunderbolt 2 20Gb/s bi-directional. There's also a 100 ft version for $529. There aren't a lot of reviews, but the proportion of reported product failures is discouraging.I understand that Ethernet is probably easier/better for connecting a whole bunch of users to one NAS, but the irony is that 10GbE connections will likely require a Thunderbolt adapter, since only special-order 2018 Mac Minis have the option of built-in 10GbE ports.
2-meter Thunderbolt 3 cables are readily available:
And long Thunderbolt 2 cables are available, too:
(Thunderbolt 2 optical cables can be used with Thunderbolt 3 Macs via Apple's Thunderbolt 3-Thunderbolt 2 adapter.)
I know there are use cases for extremely fast internal, external, and network storage. Some of those needs, at least for managing "business"-type files are reduced by "intelligent" strategies. Our main work Synology backs up to the one in the vault daily; the backup takes only minutes a day, even over "slow" 1GbE, because it's an incremental transfer. Backing up to the one connected via the Internet is slower but still pretty fast; it's automated and happens in the background "after hours" to be sure all the day's work is transmitted.