I have been using ego pen-style hardware for a year and a half since I quit tobacco cigarettes, but their batteries are on the way out and they are no longer available to buy. Also I am not interested in e-cigarettes except to give me the nicotine I still need. I find the plethora of types and models confusing and I have no way of picking an e-cigarette out of the thousands of designs available. All I need is something simple that hopefully fits into a shirt pocket (my trouser pockets are full!). Can you recommend something, including what replacements parts I will need, to last about a year?