I am involved in the 4-H livestock program here in Maryland, and was involved with it in Oklahoma as well.
I can tell you that we do not have to purchase animals from a certain breeder. The 4-H members are free to purchase them from whomever they want, wherever they want.
The goats do have to have a premise ID/scrapie tag from the breeder, or I have seen members order their own. As far as 4-H tags, those are put on when the animal is weighed and tagged for it's first 4-H show season. So our beef project had to be purchased prior to December 10, 2013, and was weighed/tagged at a county wide event on February 2nd. The goats had to be purchased prior to May 10th, and were weighed/tagged on May 22nd. The reason for the weigh-ins is to calculate the rate of gain prior to the shows. Each animal will be weighed again as it enters the show grounds.
In Oklahoma, the club traveled as a group 3 states away and purchased ALL their market animals (beef, swine, goats and lambs) from the same farm. The club leader thought this leveled the playing field by having all the animals purchased from the same place. Not so sure I agree with his tactic.
Here in MD, I can tell you that *most* of the goats get purchased from other club members who have made a name for themselves breeding and selling stock. Price is a HUGE factor. You might not be making a lot of $ by selling to 4-H kids. We all have to submit project reports, and the goal is to maximize our profits. The purchase price of the animal is a huge part of the profit. Once an animal has been tagged with a 4-H tag, it cannot be shown in an open class. Thus, it is limited to the premiums paid by the 4-H show, which are not much.
I think you'd do best by talking to you county extension office. That is usually where 4-H is based out of. They should be able to hook you up with the answers to your questions. But I don't think this venture will be one you can retire on...