Don't over look snake proof leggings or gaiters. good thing if you already have a pair of boots and want snake proof protection. Cheaper too!
More protection than that? Look at chaps
That is what I do, when I'm hunting snake country. I've got a pair I got ages ago from Cabelas, elastic at the top and bottom. They also work well when walking through wet grass in the early morning, they keep your pants legs from getting soaking wet. I can take them off when it gets hot out.
Back in So. Cal I had pair of hunting pants tailored, they were leather from just above the knees down and kind of bell bottom or boot cut. The air would circulate up your calves and were a lot cooler than something tight on the lower leg.
They say Rattlers are more afraid of you than you are of them, which is a fact most times. Twice I've had Rattlers come right at me in attack mode. I've had Cotton mouths slither right up to me or right past me, with little or no concern I even existed, in the Southern States.
I was bitten, right hand second finger on the knuckle, by a Pacific Rattler (he never did Rattle), right through a pair of gloves while clearing brush. I'm glad it just nicked me and didn't get a full load of venom in there, it was bad enough as it was. Back in So. Cal the Rattlers favored laying in ambush right next to game trails, usually late in the day just before dark.