I don't sell them myself anymore, as Velocity Arms and AirsoftParts.ca have started selling them and I want to focus on the BB product.
I'd go with the NPT charger, it has "Universal Smart Charger" printed on it. Its simple, its fast and its really safe with your batteries. I've seen it with these two retailers anywhere from $37 to $50. I believe Army Issue down in Port Credit has a few of mine left in stock at $55 if you're a walk in customer. I can't recommend these chargers highly enough. For airsoft, they are perfect - simple, safe, fast, maintains your battery's health. You can buy fancy chargers, but even if you do, you still should have one of these. My only criticism of it, is it does not come with a system to attach the charger to a car battery - I often charge at a game or out at a field like Wolfpack Muskoka and could use that feature - other than that, excellent charger.