Which Lens Adapter for the Q

I'm looking to get an F/mount (Ai , Ai-S) to Pentax Q lens adapter, e-bay has a ton of them mostly from China, but I'd rather go with a product that is reccomended from someone who has used it, any reccomendations?

I have a Nikon 400mm F/5.6 AI-S lens, whcih should give me a reach of roughly 2,000mm ! Not sure what the IQ will look like but it will be interesting to try.