Hiding self harm scars?

I self harmed for a few years and have some very prominent scars by my knee that can't be explained away by a childhood accident or anything like that. With it starting to be warm out, I'd like to wear shorts more instead of jeans, but am very self-conscious about these scars. I've tried make-up but it doesn't seem to make a difference. I use maderma but while I'm waiting for it to help them fade I'd like to be able to wear shorts. I no longer self-harm and I don't need any lectures about it, as I know it was a mistake and also have found other, healthy, ways to cope with things. I just need some advice on hiding the scars. I've found body camouflage online but can't really afford to buy them so if anyone knows of any good, waterproof, and long-lasting make-up I could find at a local drugstore, that would be great. Also, my scars are red and it isn't because they're new, as the prominent ones are relatively old.