I've been on the hunt for .223 blanks myself and I think the easiest way to go about getting more then a box of blanks here and there would be to make your own. Based on the cartridge you're asking about I'm willing to bet you're looking for a fairly high volume of them to use in re-enactments, therefore a small investment might be worth your wild.
I've been told that RCBS makes a rosette crimp die that you could use to seal off the end of an 8mm Mauser casing so it would feed properly.
I don't feel safe recommending certain primers or powder loads because I'm certainly not experienced enough to go into any detail but a google search might turn up some answeres.