Get your beard and hair trimmed, wash them occasionally, and carry yourself like you know more about the world than the dirt on your attire, and people will look at you differently. If it bothers you this much, perhaps a shave and a haircut (toot toot!) are finally due. Shower after. Grab a fresh shirt to throw on for those unplanned stops on the way home from work. I’ll bet you $5 the bike shop staff will truly appreciate it.