Wonderful topic.
A couple of things to consider before we dive into it.
Depending on where you live, there may be restrictions on receiving or shipping live plant matter to your location. There are a lot of diseases that can be transmitted through scions, so it's very important to trust your source. Since many people no longer know how to recognize these pathogens anymore, and some of them don't care, the government has decided to do the thinking for us, to keep our orchards safe. This means you may require a specific kind of import licence if you want to receive plant matter from far off lands.
It would help us if you could let us know what country you live in so we can suggest sources. For example, in the US you may wish to check out the
seed savers exchange or in Canada you may try
seeds of diversity.
The other thing to think about is the time of year. Depending on where you are, it may be the perfect time to graft or bud, but where I am, it's the worst time of year to do either. Also, commercial sellers of scion wood won't ship if the weather is too hot or cold, or may require fast, and therefore more expensive, shipping.
But that said, it is always the right season to gather resources.