How long of a screwdriver do I need to open this calculator?

It seems like my best bet is the standalone driver at this point since the screws are recessed and I don't know how far. I'm thinking the leak happened because of cheap batteries since the TI-84 is the "required supplies" calculator on school supply lists. And yeah, the kids (or parents) aren't keen to put good batteries in.

The issue is finding one that's the most reasonably priced with the cheapest shipping. Of course, Amazon is the worst of the bunch because I need to buy stuff I don't need to avoid spending $5 on shipping for an $8 screwdriver (or $10 for a set with $6 shipping). iFixit isn't much better ($7 screwdriver with $5 shipping/$25 for a set with $9 shipping), but has the best price and cheapest shipping so that's what ended up making the most sense.

The problem with not inspecting it (and cleaning if needed) is battery acid is corrosive and kills anything it touches. All I know is I'm moving to NiMh so I know this will never happen again. And yes, I think TI used recessed Torx for this exact reason. Well, that or for consistency with the classroom model (EZ-Spot) so they don't need to remember that retail gets Phillps and EZ-Spot gets Torx. If battery acid wasn't so damaging, then I may have tried the long bits.

@nick contact customer service at iFixit and request a tier level review. In light of your ten years of service to the site, you may get better pricing on parts and tools.