Lisap, I'm totally in your boat. I try on a lot of jeans that fit the way those black RCs do on GF. Honestly, the only jeans I've found that aren't too square and boxy through my waist and hips are vintage Levi's... And a couple other brands from the 80s/90s.
Current fit models for ALL denim seem to extremely straight/rectangular. And I've learned that for me this fit issue is not just a matter of taking in waistbands; it would usually require reshaping the entire back rise so it's more contoured.
A costume maker recently pointed out to me that I'm not a conventional hourglass because my curves are not in my hips, but lower, in my derriere and thighs. So conventional "curvy" cuts like the ones from Loft etc don't work for me at all -- the hips tend to poof out at the sides while still being cut too slim through the upper leg. If I could afford it, I'd commission custom made jeans, but vintage 501s will suffice.