What's the best kind of lube I should use?

:$ Okaaay. Normally I don't do this, but I really want to be safe.

* I'm a female who enjoys anal masturbation.
* I live at home with my mother, father and younger sister, so the only masturbation time I get is in the shower or if I lock my door and I have to have clothes close by that I can pull on really fast should someone knock.
* I'm 19 (pathetic, I know) and live in the United States.
* I am extremely embarassed by the thought of having to buy something like K-Y (although I already know this is my best bet). I have self-checkout at my local Wal-Mart (that GOD) but I rarely carry cash and my dad does my book-work.

So basically, I need to know if there are any household products that I can use (easily) that prefferably won't cause a mess I'll be caught in the middle of cleaning up and that I can use mostly anal.
((also, I don't know if this matters, but I'm a virgin with absolutely no plans on changing that in any immediate future, so I don't really care if it can or can't be used with a condom))

If the best answer is "Dude, you're a frickin' adult, just suck it up and buy the K-Y already!" (which, yes, I know is probably best) then that's just what I'll have to do, but I'd like to know what my options are first (may come in handy in the future too).

Thanks in advance. ;-)