There are but three major cartomizer brands, and only two of those are major players. Boge and Smoktech. A lesser player is Kanger.
After that you have vendor websites that have one of the three major companies make a carto for them to their specification, such as Ikenvape and Gotvapes.
Your choices are limited to the above. There are brand-less or no-name cartomizers out there. If you are into the buy-by-the-batch-for-less thing to save a few bucks, that might be your thing. But if you get 20 - 40 % of those being bad cartos is it really such a great deal?
Take a look at this link
510 Cartomizers to see if they have a standard size carto that you would be interested in; there's 3 pages of cartomizers to choose from. Standard size tanks are not as common as XL length cartos, so there are fewer different carts made for them.