Preface:

I am about to go on a trip to a pretty remote location where I have to pack light. 

I have read various accounts (Dvoretsky, Alburt et. al.) that there are certain positions that simply must be memorized to complete ones chess education.  The thing is, nobody (including the above named Authors) has published a tactics book that they claim is those positions.

Does it exist?  Is it for sale?  Is it thin enough that I'll be able to take it on a small plane to <undisclosed location> without having to leave my toothpaste and bug repellent behind?

This one should do fine. I also like ChessTactics for Champions by Susan Polgar or Chess Tactics for the Tournament Player by Lev Alburt; both are relatively light and worth reading.

i also have alburt's book, chess tactics for the tournament player. i like it too

I'm not sure, because I don't know the quotes from the authors you refer to, but I don't think they want you to memorize tactics positions. You should know tactical themes, but you don't learn them by memorization. I expect that they mean technical endgame positions, such as king and pawn versus king, or, a little more advanced, the Lucena positions in rook endgames. There are many more such endings, some a lot more complicated. Because they often require very specific techniques that are hard to carry to the game as a whole, they might merit straight memorization (although I haven't done too much of that myself).