You might try Casual Male XL or Men's Wearhouse , not in Bellingham, but further south in Lynnwood. JC Penney's has a big and Tall department with sizes up to 58/60, and they are located at Bellis Fair in Bellingham, but what they have in stock may be limited.
Nordstrom carries up to size 58+ online, but I wouldn't count on those being in-stock. I would ask to have them shipped to a store. The closest store will be in Lynnwood at Alderwood. For example here is an option in the Lucky Brand, popular with young adults.
One of my sons is big, too, an ex-football player, and he has had good luck at Men's Wearhouse, finding items in-stock, both with jeans and casual clothes as well as dress clothing. I would recommend looking online version of any of the stores I mentioned and then having them ship to or hold at the physical store so that you have some selection when you get there. Or, maybe you will get lucky - just call to check their inventory and ask them to "hold".