Are there any medications that help with concentration that do not require a perscription?

NO!! There are unfounded and unscientific claims for a number of substances. Any possible effect for most of them can be explained as placebo effect!
Java, java. Although not thought of as a drug by most people, caffeine has been shown to increase attention and concentration in people using it. Unfortunately, tolerance to this effect can develop, so taking a "coffee holiday" for a while can restore this beneficial effect.