Just build one of these -
That picture is about 7 years old, but the radio looks the same today. I had to replace the head unit 3 years or so ago because I got it wet (my fault, not the design's), but other than that, it's been rockin'. Needs a new battery every other year or so, but it can also be run while plugged in (using a battery maintainer). I've been toying with the idea of building a bigger one with more power, but this one gets the job done pretty well, so I haven't messed with it yet.