This flag, as well as other fake sports flags, is fictitious and is useful only to facilitate visual identification of some articles within Wikipedia. This flag has some visual elements that are similar to official logos or coats of arms of certain clubs, such as colors or some symbol, but they are NOT official and don't have any direct relation to the crest, symbol or official flag of the club. Thus, even if you consider that this symbol reminiscent of some elements of the club, this image does NOT correspond, and is not even similar to the official symbol.
Official symbols must not exist in Commons because they are protected by authorial rights (copyright); in this way, if you want to localize the club's symbol, crest or official flag, try to make contact with the club: ask for the official symbol and a possible license of use to your purpose.
Note to Wikipedians: use this flag only in a very small size, only to facilitate visually the identity of a club within a context that has several clubs together. To use it in normal or big size may induce the reader to misunderstanding. Moreover, you should use the flag only if it's clear at 20px, which is the size the flags have on many wikiprojects about soccer.
Español: Club de Futbol Monterrey