Can I borrow a calculator?

More than a hundred students enter and leave my classroom daily, and each of them owns at least one calculator.  Thus it's not surprising that calculators are frequently left, recovered, misplaced, trodden upon, etc.    I'm convinced that my room contains an aether of vacuum fluctuations which produce calculator-anticalculator pairs according to the energy-time uncertainty principle.

While I am sympathetic to the likelihood of misplacing a calculator -- after all, I left my cell phone at a hotel last weekend -- I've become ever more frustrated at the sheer number of students who wait until moments before a test to ask to borrow a calculator.  I am not the calculator supplier, but nevertheless students expect that it's not a big deal to ask to borrow a calculator.  It's distracting to everyone, and obnoxious to me, to spend ten minutes tracking down calculators, and then ensuring their return.

I snapped a month or two ago, when more students in a section asked to borrow a calculator than brought a calculator.  How to solve this problem without being a total jerk who (essentailly) says "Yes I have a calculator but no you can't borrow it because you're an irresponsible arse ha ha"?

Firstly, it's important to remember that the $100+ TI92bs or whatever Texas Instruments is currently colluding to foist upon our students is NOT NECESSARY for physics at any level.  Yes, the graphing calculator was the tool that precipitated a revolution in calculus teaching.  The ability to visualize the graph of a function instantly allows a novice calculus student to focus on slopes and areas rather than just what the graph of x^-3 + 2x² might look like.  But for physics, the older, cheaper scientific calculators are easier to use.  I've tried to spread the gospel of the cheap calculator for decades now, but students are too wrapped up in their TIs to care.

What did I do?

I personally bought a bunch of Casio fx-260 solar calculators (pictured above).  They cost me $10 each online, including shipping -- I got them from Office Depot, but they're available pretty much anywhere online.

In this new regime, I won't lend anyone a calculator because I can't -- I've purged the classroom of any "department calculators" or "Jacobs calculators."  But, students may *buy* their own Casio for $10.  I sell them the calculator in the original packaging, along with a label to put their name on the calculator right then and there.  I never chide anyone for irresponsibly misplacing their own calculator -- instead, I say with a smile, "This will be the best purchase you've ever made for physics.  You've got the best calculator in the room now."  And this is true.  

Amazingly (or not), the result so far has been more students keeping track of their own calculators.  And those who have bought have been satisfied with the purchase, as I knew they would be.  After class, when I show them the button that allows them to add fractions, their eyes get wide.  That button alone is worth the $10 to me.