Have you tried the J.Crew 1040 Athletic tapered-fit stretch chino pant? It's designed with a bigger thigh for guys who don't skip leg day -- https://www.jcrew.com/m/mens/categories/clothing/pants-and-c...
The "Athletic taper" pants from Jcrew and also the similarly named ones from Banana Republic and the Gap are great. Sometimes you can buy one size up and then have the waist taken in by a tailor to get a better thigh fit.