Investment hardware carries a good selection.
I have the 8" and they are great when you don't have a full set of wrenches available. The notches change the jaw opening by ~ 1/8". Within each adjustment notch, the jaw moves ~1/4" so all sizes are covered from 0 to >1.25". You have mechanical advantage on closing the jaws of about 12:1 so with a grip strength of 100 lbs, you have 1200 lbs closing the jaws. I've never had trouble with them slipping, but I have also never used them on something that was balls tight. If it's that tight I try to get proper tools out to do the job.
If I don't mind marking/destroying the fastener, channelocks or knipex water pump pliers probably hold on a bit better but they make a mess. Adjustable wrenches are a pain in the *** as if they are screwed in tight enough that they won't try to round the fastener when you pull, they don't go on and off the fastener well. The plier-wrenches are a great tool, the only downside is the price.