"Speaking of cheap 8mm amunititon, what manufacturers currently load this cartridge?"
Winchester still loads a 170 grain Power Point load, although it is loaded down in case someone shoots it in the old JR type (.318 inch) bore instead of JS (.323 inch bore).
Sellier and Bellot make both 196 grain FMJ and SPCE (Soft point, cutting edge) rounds loaded to full power. These rounds were very accurate for me and quite reloadable. If you shoot these in a JR bore, though, chances are you will have problems.
A brief story on 8mm Mauser -
Borrowed a Turkish Mauser, 8x57, and took it to the range to shoot. Set up a 2 litre soda bottle full of water on top of the target stand at 100m. Went back to the firing line and dropped in 5 rounds of S&B 196 grain SPCE. I wanted to see if I could get a nie big 'splat' off the soda bottle.
Well, I set the rifle on the sandbag, took careful aim dead center. A couple of fellows to my left were watching, waiting to see if the old gun could do it. I carefully squeezed the trigger, gun goes off, and the bottle is fine, but the cap on the bottle spins right off the top and flies off, leaving the bottle itself completely untouched.
Those guys thought I was Joe Sniper to pull that shot off. I did not tell them, of course, that I was aiming dead center at the time and the sights were off.
Oh, I did hit the bottle later, just had to aim about 6" low. Turkish mauser sights tend to be waaaaaay off.