Shelves aren’t exactly exciting stuff, but the Hold On Tight shelf by Colleen & Eric includes a built-in book end that can be slid to any position and locked into place using an over sized wing-nut screw system. Their website doesn’t sell them outright but you can contact them for pricing.
Grew up back East, got sick of the cold and headed West. Since I was small I have been pushing buttons - both electronic and human. With an insatiable need for tech I thought "why not start a blog focusing on technology, and use my dislikes and likes to post on gadgets."