Blank carts are sometimes difficult to find. Have you considered making your own?
I
buy my carts prefilled because the price differential between empty and filled often isn't that great. I then top the cartridge off for a few days.
After awhile, the cartridge doesn't seem to hold the liquid as well, so I pull out the stuffing, rinse in water, dry thoroughly, restuff the cartridge with the now clean stuffing, then refill the empty cart with liquid. (I also sterilize the empty plastic housing of the cartridge at that point by putting it in boiling water--but I don't boil it--just remove the water from the heat source and then dump the cartridges into the hot water for maybe 30 seconds or so.)
And after rinsing and refilling once or twice, the cartridge stuffing becomes frayed enough that I'm kind of embarrassed to put it back in . . . so then I reach for my polyester quilt batting and use some of that to stuff the empty shell of the cartridge.
There's a video that might help in this
thread:
http://www.e-cigarette-forum.com/fo...e-stuffing-m-401-carts-up-close-personal.html
The video isn't for your model of e-cig, but the basic premise is the same.
Anyway, I know it's not exactly what you asked for, but I hope you find it of some use.