Apollo patches can be roughly divided into seven categories:
Program generic patches, mission patches produced by AB Emblem, mission patches produced by Lion Brothers, Beta Cloth patches produced by Owens Corning, Recovery Ship patches, commemorative patches and patches made from designs that only existed as stickers at the time.
This last group includes contractor designs and NASA Spaceflight Awareness program 'Snoopy' designs. Some were reproduced by Eagle One Aerospace and Randy Hunt in the 90's. Most collectors don't like these reproductions. Still, they are very popular.
Although AB Emblem was the official supplier to NASA since Apollo-13, the Lion Brothers patches (priced $ 35 - $ 75) are much sought after, since these are all time original and, in most cases, are better reproductions of the original artwork than the AB Emblem versions (worth $1 to $5).
The Apollo astronauts did not wear embroidered patches during their missions, but silk screened, flame resistant Beta Cloth. Good versions of those are even harder to find (Selling for $100-$125). Rejects (misplaced colors) are sometimes offered on eBay.