Garemlin, I think Joan is right, the long cone comes with the kit.
However...
If your mom has bad arthritis, it might be a hindrance. Only 1/4 inch of carto would protrude from the cone. Plus the cone and carto needs to be removed before charging.
Further, all of the air intake is from the top between the carto and the cone. I find it too easy to "overlip" and choke off the flow. I either use the carto without the cone, or with the cone and a drip tip. Perhaps the shorter cone would alleviate both of these issues.
large cone is 1 and 3/8 inch, 35mm (included in Triton kit)
standard cone is approx 1 inch, 25mm
So the carto would extend about 5/8" from the standard cone, making it easier for arthritic fingers to handle. And at $2.50, why not give her the option?
(Maybe some nice drip tips? Halo's are $3.50. The aluminum looks great, but seems always cold. I might try a nice glass one...)
Good call. Never thought about the fact it would have to be removed for charging. She would prolly get frustrated with that and toss it aside. Drip tip is a good idea though.