If you have bald spots and just want to cover them so you don't have to worry about it all the time I may have a solution that works. I have dark brown hair and I used to get dark brown felt and trim it to fit my bald spots. With a little bit of double sided tape the patches will stay on your head. All you have to do is grow your existing hair long enough to comb over the patch.
My bald spots became so big that this solution no longer worked but my girlfriend came up with a better one. She knew about hair tracks that are sold at beauty supply stores. Usually, hair tracks are sewn into a female's regular hair as extensions. I use them to make my own custom fit hairpieces. All you have to do is cut sections off of the track and sew them onto the felt patches. Then, trim the hair to look like your haircut, put some double-sided tape on the back and stick them on your head. You may need to have them trimmed by someone who knows how to cut hair really well.
If you want to see what mine look like check out my photo blog. I have a picture of the front and back of the pieces on there. Let me know if you need help.