What you want is an AC to DC adaptor, that does 15v, and (going on the 2.9A assumptiomn) 3A. Having more current available is not a bad thing (Less is), but the voltage (generally speaking), must be the same. You *may* be able to get away with .5v either side, but 15v is fairly common for, say, a Universal Laptop AC adaptor. These will generally be capable of at least 3A, (90W).
Most will come with a variety of tips that fit on the end. if one of these will not fit, you can take the 2.5mm tip included in just about everything, and make up a short flylead using the tip off the deceased Adaptor.