B.357;
There's a good choice available, what do you want to do? Tikka makes selected guns in LHB, as do the others mentioned above. CZ makes a couple of the .22 rimfire 452's with left bolts too. CZ also recently released the LHB 527's in .223. I'm hoping to see the 550 come out in the next couple of years.
Or, do you want to build from a bare action? Montana Rifle Company, MRC, produces both LHB Mauser actions and barreled actions. Their actions closely resemble the Winchester model 70 action, as do the Dakotas.
If you don't mind used, there are a couple of versions of the Remington 788 with a left bolt. I do believe they're found in 6mm Remington (a helluva good caliber), and .308. Also, Winchester made the Classic in LHB in quite a few calibers, but expect the price to be substantial. A very few Zastava Mausers were imported under the Charles Daly brand in .223 and .30-06.
Hope this helps. 900F