Being a long-legged moderately skinny myself, I also have some problems finding jeans. The brand I really like right now, that is a little pricey, are Levi Capital E. They have a great variety and lots of great boot cut styles, and Levi has this handy thing called Jean finder, You answer some simple questions such as how you like your jeans to fit, and what leg opening you want, and they find you jeans based off that. Another brand of jeans I am rather fond of are Hollister, mainly because they have jeans in long, and they are defiantly long. They also have a wide variety of flared jeans and boot cut.
I have seen inserts for the side seam to enlarge the waist. If the adjustment is not a lot, you can get some jean material from the fabric shop, make a wedge shape from the fabric, allowing for seams on all sides. You will need to remove the waistband in the area of the side seam, cut it so that you can add