Hot knife, coping saw, three sticks of crisco, 2 pints of bourbon, one inflatable animal (your choice), duct tape, and a copy of the special episode of the golden girls ...
Mightn't make the best hole, but it will raise some eyebrows when you take that stuff through the checkout at WalMart
BTW - With the Dremel ... use the fibre cutting wheels. They disintegrate faster, but you get a better cut on plastic. Also, score along where you are going to cut with a utility knife first (help minimise chipping - shouldn't happen, but occassionally does). Remember it is better to undersize your cut, then grind it out to correct fit, than to try to fill in gaps.