The retro bowling-style button up shirts commonly worn by Charlie Sheen's character Charlie Harper on "Two and a Half Men" can be found at BowlingConcepts.com and DaddyOs.com.
Sheen's shirts on the show are typically distinguished by a polo cut, asymmetrical patterning on the front and, occasionally, contrasting colors on areas like the shirt sleeves or pocket. Alternately, fully patterned Hawaiian-style shirts appear in certain episodes, which are also available from the sites previously mentioned. When Sheen's character wears undershirts, they are usually Hanes brand. This was due to his position as the company's spokesperson at the time the show was filming.