I had seen another post with carts in an ammo box here, and I went to the sporting goods store the next day and bought two. They work great. As to filling with the syringe method, I thought the same thing as was earlier posted; the carts sit snugly in the ammo box so it would be easy to syringe fill. Now I just need my syringes.
The ammo size on my box states 45, but the first box I tried had a flat lid and the carts didn't quite fit. I found another ammo box that had a deeper lid and they fit great.
The guy that helped me asked me what caliber when I asked about the case, and I held up a cart and said, "this caliber". When he looked at me with his eyebrows raised I smiled and said, "I'm a vaper, not a hunter". 
