Here is a decent one that I used. It's for the E46, but BMW doesn't change much over the years as far as internals goes. They stick with what works.
If you are mechanically inclined, it's a very easy install. Should take one person about 3 hours. Only use one of the hydraulics to open the trunk and keep it open. Using two causes it to catapult objects far distances. I didn't need to modify, cut, grind, file, or sand my iCarbon trunk. Everything just bolted right up. I would assume it would be the same for a high-quality company like Slek. Haha