What home printer is capable of printing on board book pages
After about a week of scouring the web I found a forum that mentions using an HP Photosmart Pro B9180. This is a semi-pro printer. It has an option for a straight paper path and can print on items up to 1.5mm thick which is enough for my 42pt paperboard media stock. 

It is no longer made so you have to go to the used market. Refurbished units seem to be about $400. Not cheap but certainly better than the $1000-20,000 pro versions.

Con: this printer is not for amateurs and guzzles expensive ink.