anything between a 7 x 40 and a 10 x 50 . That is a good mix of power and objective diameter. Look on ebay, but also check it against this site , www.durhanoutdoorsupply.com . They have good prices and free shipping on a lot of stuff. There are other sites too, if you care to compare. Optics planet, the optic zone ... and I have heard great things about vortex binos as far as quality compared to price . I would definitely check them out.

Good Luck