Okay, an update on my search..
I requested Red Ants Pants for Christmas, but the rest of the family looked at the price and laughed at me. So, using a dusty Eddie Bauer card I have now ordered the Alpine Pro pants, which come in woman's tall (which is pretty rare) and are also available in larger sizes (most other brands seem to top out around a smallish size 14). I have my fingers crossed that these pants will fit and I will just need to hem them. Bonus - only $10, net, out of my pocket for them and I can return to the local store (but can't get my size off the shelf...)
Note, they will not be useful for construction -- only hiking / canoeing / camping.... I guess I will have to either keep wearing my old men's construction overalls (honestly, two people could fit in those things..), or keep buying second hand jeans for $8/pair and wear them out continuously.
Anyway -- I noted that Eddie bauer has many men's pants that might work for you, too. Some do have articulated knees, and have a stretch fit so maybe gussetted crotch is not needed?