Factory Hornady brass is going to be hard to come by unless you buy their factory loads or do like one poster said and go on the online auctions and bid for it. Of course, you can do like another poster said and fire form your own out of Remington .222 Magnum brass. I have worked up a fire forming load with 32 gr. Hornady bullets that shoots in the .5" to .7" range for 5-shot groups, so I will take some of those out and do some prairie dog shooting with them.
Redding, Forster, RCBS, Hornady, Lee all make dies for the .204 Ruger. I think there are a couple more that do too. Bullets can be had from Hornady in 32 and 40 gr. V-Max, from Berger in 30, 35, 40, and 50 gr. The first two weights are FB HP, and the last two are the Length Tolerant bullets and are boattail bullets. Unmussig makes the 35 and 40BT bullet- someone bought the Bill Lucas .204 bullet making dies and they should be up and running soon and you can check at this site for updates on that situation:
Lucas bullets Remington has factory loads for the .204 Ruger using their Remington Premier AccuTip-V boattail bullets for both the 32 gr. and 40 gr. stuff. I don't know who makes their bullets, maybe they do???
I bought a bunch of those "blem" bullets in the 32 gr. weight a while back. I haven't tried them, but they all look like the same thing as what comes in the Hornady bulk bullet boxes. I can see no flaws in them. I haven't weighed any of them, but they should be good varmint medicine regardless.