If you use Clorox Regular unscented bleach, then that is generally now 6% bleach while off-brand Ultra bleach is 6%. On the Clorox Regular, it says "6% Sodium hypochlorite" and also says "5.7% Available chlorine" and is what you want. I'm not sure if the off-brand Ultra bleaches label their chlorine content.

In Canada, Clorox has an Ultra bleach which is 6% while their Regular is 5.25%. Generally, you want the highest concentration bleach you can find as that's less weight to carry, though you can compare prices as I describe below. Also, Clorox bleaches have the lowest amount of "excess lye" in them so have a smaller effect on pH long-term compared to most off-brand bleaches.

If you have a local pool store or hardware or big-box store that carries chlorinating liquid, then that could be 10% or 12.5% or something like that and is another option for you. It's the same as bleach -- just more concentrated so is less weight to carry. You can roughly compare prices by computing the % per $ cost for the same quantity, so if 6% bleach cost $1.25 for 3/4 gallon, then that's $1.25/6/0.75 = 0.28 cents per % per gallon while if 10% chlorinating liquid cost $2.50 per gallon, then that's $2.50/10 = 0.25 cents per % per gallon so would be a slightly better deal.

Richard