I’m looking for fanned enclosures that use Thunderbolt 3 connectivity to house a high capacity 3.5" hard drive which will be used for backup purposes.
Any suggestions gratefully received…google seems only to return advertising rather than decent results.
Look on macsales.com … akitio is one but some are multi drive bay units this won’t work on ROCK and NUC unless you use Windows perhaps. Macs of course no issues.
I don’t use an enclosure, I use a “toaster”, or hard drive dock for that. Easy to switch between drives to have a rotating backup. I think the one I went with is Pluggable: https://plugable.com/products/usbc-sata-v
However, this might suit you. The site has a lot of enclosures, you should take a look.
Thanks chaps, I think I found what I’m after.
That is more of a DAS than a hard drive enclosure (which I always think of as a single drive).
I have a 4 bay stardom tb2 drive that can do several raid config but also looks like 4 individual drives. I used to put a 1tb ssd drive in one bay and raid 3 other spinning drives in the rest. Worked great for backups and cloning. Could even boot off it. Mac only limitations with the raid I think, but I never had a windows box with tb support to try.
It is, but I couldn’t find a 3.5" thunderbolt 3 enclosure
Frustrating that as soon as you look at a multi drive solution they assume you want raid.
Try It! You’ll Like It!! 
My lastest mobo is a keeper, I’ve been impressed!: https://www.gigabyte.com/us/Motherboard/Z390-DESIGNARE-rev-10#kf
But, then again we are playing around in the area where a motherboard alone can cost as much as some of the NUCs people argue over. Heck, that Akitio enclosure is more expensive than some of these NUCs.