I do not think that they sell parts. It may be more efficient to buy more sticks. Time is worth something, and it would be hard to get a good standoff made in such a small quantity. It is hard to get anyone to do anything these days. Good people are working and have enough to do and the rest do not want anything to do. Welding a stick together is economical if you can weld aluminium.
Even a welded stick with all the hardware will cost well over $30 before you are done and double that if you put a cam cleat on it. Dan Infalt sticks are not an unreasonable price to IMO> Compared to making a stick. Or buying and modifying a stick. His sticks will have fixed steps and be longer than you might want. They will be 9 inches wide and stack well compared to a helium that is probably 4 inches wide folded up.
Also if you desire a cam cleat can be side mounted on a Infalt stick if you want. That is not possible on a helium. If you put a cam cleat on a helium on the top side of the stick they will not stack really well. Cam cleats are simple and safe - I was thinking of your daughter.
When the Infalt sticks come out they will likely be the best stick you can buy... unless you want folding steps then I would buy the helium.
I have tried them most of the available sticks or at least seen them. I have only seen
@Dewey Infalt sticks in pictures. They look good.
There is not perfect a option IMO. I like the ones
@bowhunter15 made and
@flinginairos - two good options. I have done something similar.