Maybe get him a happy to be with you card? Or one that says you're thinking of him. Does he like flowers? Does he like baseball? Football? Hockey? Get him a hat for his favorite team or you can gift him some corporate gift items.
I have the same issue! My boyfriend will not tell me what he wants. He said that he wants something that he can wear that shows how much I love him...? I don't really know... Get him like cologne or a t-shirt. Maybe an inside joke you guys have...? A picture of you guys in a frame? Or just take him out to a nearby food place and pay? Those are some of the things I might be doing...
Make a home-made card......guys seem to like those!!!
Make him a homemade shirt. If done right it'll turn out super cute and if hes like my bf he'll love it