Isopure has a zero carb whey powder.

FWIW - going too high on protein will cause the excess to convert to glucose, which will stimulate an insulin release (hopefully small) and possibly kick you out of ketosis. Not a big deal compared to actually eating carbs, but you should be aware of the effect (gluconeogenesis). Try to stay under 1g per kg of bodyweight to be sure - should be safe at 100g or less for your weight.