Quest to find the material to renew these much-loved trousers

These are a much-loved, store-bought pair of trousers which I've worn summer and winter for some twenty years. I want to make a new pair that looks and acts just the same, ie hangs and moves as beautifully, as liquidly, feels so comfortable - and is as serviceable. 

The material is some sort of twill, mostly cotton I'd guess with a synthetic element added. It feels soft, a little like chamois maybe, maybe helped by years of washing, and it doesn't need ironing. It's not hot even in the middle of the Australian summer, yet it also has a lovely weight. (The trousers weigh 426 grams total) 

Can you get an ideas about which of your fabrics would do the trick, without actually feeling the trousers? I'd like to make a pair very like this pair ...and then another few pairs in different colours, same sort of material. 

After that, I could possibly even try a different weight too for fun. I'm open to suggestions....

Thank you!

Warmly 
Chris