Surplus ammo, if any were readily available would be an obvious choice, but I've not seen any around for some time. MFS made some 30-06 FMJ ammo, but again, it's been a while since I've seen it anywhere. However, when I had some about 20 years ago, I remember it as being quite hot and I had a few blown primers. Other than that, I think Hornady had some proprietary .30-06 ammo they were making. Right now, as far as I am aware, guys I know with Garands are rolling their own ammo.
Edit: Someone beat me to it...I was going to mention Prvi Partisan.