Call for Content: MatCaps - User Feedback - Developer Forum
Material (MatCap) Generator (Texture)
163 FREE MatCaps by SEspider on DeviantArt
FREE MatCaps, silver and white ball, png | PNGEgg
SFDEMIR - ZBrush MatCap Material Collection / 10 Unique Material
I modernized the red car paint matcap from 2.7 which works very nice for checking reflections. You can install it in 2.8 via the lights tab in the preferences. : r/blender