Thanks all for the recommendations for skinny sweatpants. We found 2 pairs for DS that work after many discards. Now it's on to the jeans search. For a few years Old Navy skinny jeans were the go to. DS needs size 10 for length but the waist and crotch area are very baggy on him even with the adjustable waist pulled all the way tight. I'm taking him in to try their Super Skinny Jeans as those have worked too, but I think it'll just be the same waist/hip with a skinnier leg. They have slim fit skinny jeans, but are sold out in his size - He may just have to wear his size 8 jeans that are getting too short until they restock the slim skinny jeans.
DS is growing taller but his waist, hip measurement isn't changing. He needs size 6 jeans with longer legs!!!
I'll also try Gap, the Shawn White brand at Target and H&M. Anywhere else to look?