Cheapest place to buy a new tuner for my 8000

[tw87]

Just set up a spare dish I had to 13east and have decided I want make use of one of my spare tuner slots in my 8000.

Where can I get one at a decent price?

Are they the same as the tuners in the 800?

I'd be wanting an HD tuner so I can make use of the HD channels available.