I have something like this on my bikes:
Picked a pair of them up at Walgreens for less than 10 bucks.
The mirror is convex and twists so you can adjust to whatever angle suits you best. They work great, but habits are habits, and I still twist my head around and get a quick glance.
The link that the OP posted? They want 30$ a piece for theirs. These look like the same thing, only not so expensive.