ive heard you can get scraps from some of the audio shops
back off topic, mouse those big lights draw a ton, i would do an alt before a battery for those lights your not going to be running them with the engine off you dont need another battery anyway. maybe if your going to be doing some winching, other trucks of course. i had 4 kc'* on my old jeep 100w a a peice at 12v thats 33.333 amps just going to the lights. add to that your headlights and the alt isnt putting out much at idle where most off roading is done.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock