Why is it a pin? Granted, not a lot of room for a weld on a lot of them unless you go to an MC. But if there's room, you can weld all around and fix it. If you're worried about local deformation of the cross section neutering the fixity, add a web stiffener.
Otherwise, a plate or angle off the web and welded to the base of the post. But beware, this can extend your post several inches and some standard sizes may not work.