When you have 5 posts/replies and wait about an hour, you could ask in the Blu subforum
Blu Electronic Cigarettes
There is very little selection of prefilled cartos for 510. For 510 blank soft-cap cartos are usually used and filled with whatever liquid you want. People who want prefilled cartos usually get KR808D-1 aka Vapor4Life
There is a big thread about the cartos in the Blu subforum.
BTW - you can refill your Blu cartos as long as you don't vape them dry and singe the stuffing. So if you bought a simple flavor like vanilla or bought a tobacco flavor you like, you could keep it damp with any compatible flavor ejuice. Like you could add fruit flavor to either - for a while the tobacco would be a fruit flavored tobacco and eventually may be mostly fruit flavor. And just about anything will blend nicely with vanilla. You should be able to get days or even a week's use out of a carto. Check that Blu section - I'm sure they discuss refilling.