Intel partner Simply NUC offers a wide range of passively-cooled NUC, including vPro enabled Dawson Canyon and Provo Canyon (AKA NUC 8 Pro) units. Their in-house cooling solution is the aptly called Porcoolpine chassis and does look great. The diminutive systems are fully configurable and the Ubuntu installation is free, which is a nice little touch.
Source: Simply NUC
