hey mate, there a few options for an octave up pedal. depends how much cash you wanna blow really. the ehx hog's (or it might be pog's can never remember which is up and which is down...) get a lot of attention but also a fair bit of cash. if you can get your hands on a bass whammy it should do the job. i've also read good things about the joyo ultimate octave (
JOYO Effects Pedal - ULTIMATE OCTAVE **+FREE Picks** | eBay)if you want a cheaper option, but havn't actually heard one in action.
there are quite a few more options than just those i've mentioned but i think they seem to be the most popular, from what i've read anyway