Wireless adapter for guitar on rockband?

I bought a new ps3 slim at best buy, and my dad said he bought a rockband set from a garage sale so i was like, What the heck, let's give it a try. It worked perfectly for the drums and the mic. But with the guitar, the previous owner lost the wireless adapter that goes with the guitar. I went on craigslist to see if anyone would be selling the adapter around my area, and there was no one local. I can't order from ebay because my parents do not allow me to order anything online (don't know why) so is there anywhere else i could find this adapter?