Not sure if this would count as "something he can carry with him" but my guy is also a gamer geek and a few years back I made a set of Four sided dice for him that could be hung from his rearview mirror. (The idea was a twist on the cliched six sided dice that many people hang from their mirrors.) The four-sided dice are the ones that look like a pyramid, so you need to cut four triangles the same size and sew them together. (I originally wanted to do eight-sided but they kept coming out too big.)
My dice were made of plastic canvas and wool, a light (manly) colour for the background and numbers backstitched on in black (embroidery thread or wool). To make them more Valentine's you could replace the number "one" with a heart stitched in red. You could also make the dice with fabric and stuff them, or probably sculpt them out of Fimo.
Anyway, these were a big hit and stayed hanging up in the truck for quite a few years. Eventually they came down when we sold the vehicle and saw how sun-faded they'd become, but I know he's still saved them in a drawer somewhere so they definately touched his gamer heart.
As I said, mine were intended as a rearview mirror hanger, but maybe you could make them small enough to be a key chain.