backlight control
First off, you need to put a 1 ohm resistor in series with your trimpot, else when you turn the pot to the high end, your backlight will go up in smoke, poof. You can get a 1 ohm 1W resistor at Digi-key:
http://www.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=ALSR1J-1.0-ND
Next, you don't say any details about the pot. A trimpot implies a board-mount, screwdriver-adjust, device, and you can get them in 1-turn, 3-turn, 5-turn, 10-turn, and 20-turn. You will still need a 1 watt power rating so you don't fry it when its turned near the high end. 1 watt trimpots are not too common, but you can get them at Digi-key too. Or you could choose a panel mount pot with a shaft, these are much more commonly available in a 1 watt rating. Then you get to choose the type: wirewound, cermet, carbon comp., etc. So, if you decide on the detail, I can steer you to a part #, or you can search the site yourself. Pots will cost anywhere from $5 to $50, depending on type.
