Great question.
It depends of course on how many pins you are looking for.
The more you buy ... the cheaper the price.
There are several companies out there that will help you to custom design your lapel pins. They offer this as a free part of their service. The question is how many are you needing. If you are looking for under 250 pins then any lapel pin wholesaler will work for you. Simply type in "Custom lapel pins" into your favorite search engine.
On the other hand if you are looking for MORE than 250 pieces you can actually BYPASS the middle man and get them straight from the factory. One source you can look at is http://littledragonpins.com . By dealing with the same factory that often makes the pins for the lapel pin RESELLERS , you can save 30% or more. This can add up to a lot of money especially if you are working with a fund raising organization. I am sure that you want every dollar donated to possibly go towards helping them out.