I recently made our number rods. These took me about fifteen minutes. They would certainly be easy enough for an older sibling to make.
I could have photocopied the page from my book, but I decided to make mine just a little bit bigger.
I realized as I was coloring them that I could have eliminated the spaces between the rods and saved myself some trouble in coloring and cutting.
I think the book suggests painting balsa wood, but it seemed easier to me to use some left-over poster board and just color it in with crayons.