If you want the ability to order the exact number of rootstocks you want, you may have to wait.
But for example, this place: http://www.ripleycountyfarms.com/rootstock.htm
Looks like it might sell you a bundle of 25 Lovell rootstock right now. Im not sure if that company in specific will help you, but you could probably contact places like this, who might Only sell their rootstocks in bundles, but for many people, the price of around $60-70 may be worth it for the ability to start your trees this year. (Plus extras for friends, lol!)
Another thing you can do is troll your local nurseries and Big Box stores to find some cheap peach trees, cut off whateverās there, and just use it for the rootstock.
Just tossing some ideas out thereā¦