We love the rio knickers - the monkey bar knickers & there is another cut but can't remember the name.
Thick elastic, never worn down, DD1 is quite thin and the fit well.

I cheat and get them from dimmeys when they have them for like $1 - $2 a pair in the 2 packs.

So much so we bought the same for DD2 and the refuse to wear the old plain cotton ones.

The ones we get are the cotton/elastane