Help me E-cig experts!!

Hey guys and girls,
I don’t smoke e cigs but my bf does. He is an e cig pro and is constantly smoking one and buying new juices and all that. Well his bday is coming up and I want to get him a new really nice e cig. His current one is a medium sized one that he unscrews the top to load the juice in. I think it’s two pieces. So id like to do one similar to that but nicer. He always gets me the best bday gifts and I wanna repay the favor and I know he’d love a new one. I just wanna make sure I find a good one. Can anyone help me? I’m lost looking at these things. I really appreciate it!