L.A. Computer Company offers offers the LMP 7-Port USB-C Attach Hub for iMac with Thunderbolt 3 for $44.95 with free shipping. That's $10 off and the best price we could find. It's compatible with the 2017 21.5" iMac and 27" iMac/iMac Pro and requires one Thunderbolt 3 (USB type-C) hub and one USB 3.0 port.