Justin Wilkie Shared this over on the Facebook page.

Combined cable and hydraulic caliper which allows easy integration of a cable operated handbrake. (Much easier than installing two separate calipers).

Search for buggy / ATV / Quad calipers and you should get a result on your favourite online shopping store. I just ordered one from this ebay advert - https://www.ebay.com.au/itm/133121232020 

This one is a 90mm mounting, which is physically larger than the standard calipers and has a lot more pad area. Will let you know how it works out.

Thanks for the share Justin 👍