hook them in parallel.
any 12v adapter will work...the fans are very low draw (is it really .08 amps??? the computer fans I've used are closer to .1 to .2 amps.) so 4 of them will probably be less than the rating on whatever adapter you find.
the best adapter (unless you are going to recycle an extra cell-phone charger) is one that gives you the choice of multiple voltages. I use an adaptor I found at Amazon--Coby 800mA Adaptor (part # CA-989) that gives you a simple switch to choose between 1.5, 3, 4.5, 6, 7.5, 9 or 12 volts. The speed of the fans varies with the voltage (the wonders of direct current!) so you can better control how much cooling you get. (I think you could get the same effect on a more DIY basis with a potentiometer/variable resistor.)