Looking at the amount of slack in that chain you would take a couple of links out as it is. you may just then need to add a half link. Just go up the local skatepark and speak nicely* to the local BMX'ers they are bound to have a couple in the toolbox.
*(just nicely, not a creepy Jimmy Saville type nice, that could get you into trouble)
Jamie
*(just nicely, not a creepy Jimmy Saville type nice, that could get you into trouble)
Jamie