5-channel IR line sensor plus front (?) IR proximity sensor plus bump switch in one package for about $3.15 USD shipped (Oh, plus tax now!). Might need a bit of rework since the front IR sensors hit the wall before the microswitch.
But an interesting little sensor array, all wired up to a convenient connector. https://www.ebay.com/itm/223263216001
I for one, would love to see a Boebot/Activity bot with high speed servos do impressive speeds on a line following course. It would take a sensor like this to do so.
BTW, there are those who consider line-following as the "holy grail" of robotics: https://www.wiltronics.com.au/MeetEdison/
, about a quarter way down the page.
"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."
- Pablo Picasso