It depends on whether you want to make them yourself or buy them. If you want to make them yourself, street sweeper bristles work well (just follow a street sweeper on a bicycle and you'll get a few), as do the strips of spring steel inside of windshield wipers. Then, just look up some tutorials on how to make them (I'm sure youtube has a few decent ones). If you want to buy them, Southord has some really nice sets, and I personally recommend the PXS-14 for a beginner (I use it daily).