I'd go with a Marauder and tank setup. If you're in Florida there'll be plenty of scuba shops around to fill a tank for you. You can pick up a used tank for < $100 that'll fill your rifle around 80 times, and depending on the caliber, get you 24 to 50 shots per fill. The smaller calibers use less air per shot and generally are a bit quieter. I love my .25 Marauder, hits hard and very accurate. I don't know how hard lizards are to kill so not sure you need a .25?.
