Hey Tina, If you let us know what country you are from, im sure we can suggest a few suppliers in your country, otherwise check the Sponsoring Suppliers link right at the top of the page..
The 901 is a good option, Its a bit longer than a normal cig and the filter end on the new style 901's are kinda whistle shaped but its the one most people rate as being one of the best, also with readily available parts. The M401 is also fairly well accepted, its much more cigarette like but it sacrifices cartrige size for looks, so you will find that you change cartriges more often.
Hope this Helps
Ed