The SP is already incredibly small. I took a look at a motherboard scan and there are components from end to end so no, most likely not. If you're putting it in a calculator you're probably better off putting a Raspberry Pi zero inside. You'll be able to play more games but it'll be a little more challenging since you are building a new unit rather than changing just the casing.
If you are set on using an SP then you can remove components to see if the handheld still functions when they are gone so that you know what can be removed and what can't rather than just blindly cutting and hoping for the best.