Couldn't an old (or a new?) HP graphic calculator do the job? It's not technically basic, but you can do tons of stuff on it in addition to arithmetics and function plotting - including programming games, etc.
Plus, it's organized as a LIFO stack. To do e.g. 2 * (2 + 2) you'd enter: 2, 2, 2, +, *. Which helps train the mind to think far ahead about what you want to calculate and how.
Plus, it's organized as a LIFO stack. To do e.g. 2 * (2 + 2) you'd enter: 2, 2, 2, +, *. Which helps train the mind to think far ahead about what you want to calculate and how.