I purchased a lefty Iceman bass kit a few years ago from this place via ebay. I have yet to build it, being the lazy SOB I am, but I was impressed with the quality of the parts supplied. So someday soon I'll get around to this. They have other unique designs typically not available lefty (Explorer, Iceman, Flying V, etc.), and all of their kits come left handed.
Here's a video review of their '51 P Bass style (a lefty too), which is out of stock now but apparently will be back in soon. I encountered none of the neck pocket issues he did on mine.
https://www.youtube.com/watch?v=pXdHxyBhrhQhttp://www.bargainmusician.com/diy_bass_guitar_kits