Need help figuring out lighting!

Hi everybody! I don't currently have a bearded dragon but my best friend's 13y/o younger sister does, and she's lost interest in taking care of him as so many kids unfortunately do, so I'm trying to prepare to take him into my care to give him a better life. I've had pet snakes in the past but never a lizard, so I've been doing a ton of research into what a bearded dragon needs to thrive, and I had some questions about where to find bulbs for his UVB lighting! From my understanding arcadia and reptisun (NOT reptizoo) are the best brands for this, but I'm struggling to actually find both a light AND a fixture online. What's the best place to buy UVB bulbs and fixtures in your opinion? Ideally I'm looking for ones suitable for a 4x2x2 enclosure, since that's the size of the cage I want to buy him. Thanks for your help in advance, and have some lizard pics as compensation!