I think Remington still makes loaded ammo for the Maximum but I don't know any sources for just brass. Maybe someone else can give some info on that.
My favorite load for the max is a Speer 180 35 cal flat nose rifle bullet, loaded with 23 grains of H110, CCI400 primer, seated to the cannelure for an overall length of 2.15".
This is the most accurate load I have ever fired in every one of the Maximum chambered firearms I have tried it in.It will cloverleaf at 50 yards and it remains above the speed of sound past reasonable hunting ranges (125 yards).