How to get Doctor Note to take medical leave for cheap?

I work part time so my company doesn't provide medical insurance for part timers like me.

Recently, I tore my muscle in my knee. It's not a serious. It just need time for weeks to recover. I don't want to spend money to see a doctor on a case like this. Sometimes, it's difficult to ask a doctor note for medical leave.

How can I get doctor note online or somewhere in Houston for cheap?

Thanks