Do you have a lot of extra biker patches sitting around? What do you do with them? You might put some on a second jacket or even put them on things like reusable shopping bags or decorative pillows. If you have even more patches, though, especially if you have duplicate ones, you might think about trading them with others. There are a few different ways you can go about this, but the main thing is finding people to trade with.
One of the first and easiest places to find bikers to trade patches with is at your local motorcycle club. Your fellow riders will probably be looking for patches themselves, and they may have some to trade. Even if they don't have the patches you're looking for, they might know who does. They may also be able to direct you towards a company that sells embroidered patches.
Another place to look for possible trades is on biker-related message boards and online forums. Your local friends may not have access to the patches you want, so you may need to look farther away. Bikers from all over the world use online forums to chat about bikes, riding, and to trade and sell items. You might get the patches you're looking for from a biker in Japan or Australia!
Finally, you can take your patches to biker rallies and try to trade them with people there. In a way, a rally covers all three bases: you'll be able to talk to bikers in person like you would with your local club, but you'll meet bikers from all over the country (and maybe even from other countries) at the rally. There are also patch vendors at these rallies that may be willing to trade patches with you, especially if you have some rare ones.