Angie, you're such an inspiration --- so nice of you to share this hunt on the forum for those of us still trying to get a handle on PPP. You're a saint!
Unfortunately, am no help with the hunt --- it's not that hard to find the thicker, non-stretch fabric in India, as long as premium tailoring is not required. All one has to do is pop into one of the supermarket or departmental store own brands, or in some cities, like Delhi, get some made to order from a local tailor. I've never had luck with either of those since I'm not an easy fit and don't have a 'just-so' sample I could bring to the tailors either.
I do sympathise with your hunt though, since I often find I'm also chasing something a little elusive since the 90s --- I want soft, thick, minimally stretchy, mid-rise (that becomes low in front but stays higher up in back on me), straight or skinny legs (but not too tapered) that still fit, dark jeans with just a slight fading on the thigh, and back pockets. That's the ideal, and I haven't found it yet. The closest I got were my Benetton bootcuts in the early Noughties, but they don't have back pockets though the back darts helped with fit immensely. Bizarrely, my Mothercare maternity jeans actually have the right fabric, even though not the colour or shape I'd consider optimal!