Soundigital - 1000.4AB, 500.4AB
Incriminator audio - IA6.4
MB Quart - Onyx 4.125
Soundigital are somewhat pricey but they will work for sure.
MB Quart can be had for about $160 on ebay. I personally have one and have tested this one. I have made it come on and play music on voltage up to 19.4V.