And if you search for #coloringpages on social media, you’ll find lots of artists making their line drawings freely downloadable, for the same purpose.
But I went through a bunch, and there’s nothing industrial-design specific. The closest I found are these line drawings of cars by Abimelec Arellano, the concept designer who did those “What If” car renderings. Arellano writes:
“Some great people have converted their artwork into coloring book-like pieces to aid the #stayhome situation and keep the younger ones entertained, so I thought I’d join in and post some of the cars you’ve seen here ready to color! We have the Rambo-Lambo 6x6, The Hellcat Cuda, The slammed Grand Marquis Wagon, the F40xbody, and the Hellcamino.”
Here they are, if you guys wanna add some color. (You can download larger versions here if necessary.)