For regular children's or adults leggings we usually use 180grams cotton/elastane (95% cotton, 5% elastane). But this fabric would be too lightweight for your needs.
When making jeggings we usually go up to 230 - 240grams (as they're winter weight), and they're usually poly/cotton/elastane.
I guess I would try to find something like that - a heavier weight cotton elastane or even nylon lycra. Nylon is usually used for swimwear so it's a bit more slippery. Cotton elastane would be a lot easier to sew, but you may not find the weight that you need.
I suppose you could always use a French Terry (that's like tracksuit fabric). It's usually 260grams so will be thick enough to not be see-through and it's nice and easy to sew.