Look no more:
https://www.fjallravencanada.com/keb-trousers-w.html
These do come with a hefty price tag but they have a lifetime repair warranty on them and then some:
- 50 years of field testing (this brand has been making hunting clothes in Sweden for a long time)
- Stretchy waist, hip, and knee area
- reinforced butt, thigh, knees and boot area
- removable knee padding slots (knee pads separate)
- hip and calf zippered vents, to dump heat
- many pockets and loops for gear
- waterproof (except around stretchy hip area but that's DWR)
- Buckles to secure to hiking boots
- free waxing to further waterproofing
- free repairs
- free hemming
The only downside is most sizes are sold out everywhere in North America, and the earth tone colors are discounted for Spring Summer.