They sell direct: http://www.track-it-tv.com/
Don't know if they sell through any distributors or not. Here are some installation tips.
I installed mine, then just called up DirecTV to come install the dish, etc. The Track-it TV unit MUST be level to operate properly. They send you a little level to use during installation. There are two wires coming from the unit, AND there will be two cables coming from the dish, so allow plenty of wire run diameter... I used 1" conduit where I could, and loom tubing to cover the exposed wires where I couldn't.
The two wires coming from the unit are your 12V power, and a six conductor phone cord. While you probably won't need to cut and splice the phone cord, you'll need one of those tools from Radio Shack or wherever if you decide to shorten that cord. Regular 12V wiring specs apply. You'll need a readily accessible switch to turn the power to the unit off and on. No need to have it powered up except when you're re-aligning the dish, at anchor or underway. Just sitting at a dock you don't want the power on to it, since it will sort of "hunt" just a bit... you don't want A. the power drain or B. the wear on the unit.
Once that's all installed and the satellite dish folks come out, make sure they put a splice on both of the cables a foot or so away from the dish. They can do it a lot better than you can (I bet) and have really high quality splices. That way, if you ever have to remove the dish, it's easy to disconnect the cables. Of course, at that point you'll have to cut the 12V and phone wires, and re-splice them later. That is, unless your installation has all that wire just easy to remove. Mine wasn't! As with any electrical connection, get up there and spray the splices with corrosion block. I also covered* mine with shrink tubing.
The hardware on the dish isn't exactly marine grade. You should probably spray it with something like Boeshield, CRC, or something sticky. Either that or even spray galvanizing. They will rust over time, and you know how dealing with rusty bolts is.
Oh yea, as with any consumer electronics on board, make sure you power it through some type of surge protector for the receiver unit.