Hi There! What seals it when you recieve the carts? On my 901 carts, even the blanks come with a little rubber end cap. I save them to seal up my refilled carts when traveling.
If your carts don't come with the rubber end caps, maybe you could use a snack baggie to carry them around. Or howabout a small bottle and drop a couple in.
I fogot to welcome you to ECF!