Brandywine Porsche in PA aways seems to have Litronics for sale on eBay (
http://search.ebay.com/_W0QQfgtpZ1QQfrppZ25QQsassZbrandywineporsche). Expect to pay around $1200 shipped. Don't pay more than that for Litronics.
To have them installed, the dealers around here quote me about $500-600. You can install them yourself in 5 minutes if you don't need the leveling stuff. And it is to my understanding that the retrofit kit doesn't technically level the lights... it just repositions the beam when your brights are on.