If you had a bunch of notes of your own you wanted to carry with you, you could try printing them out with a laser printer in a very small font on transparency material, or some other water-proof material. A 300dpi printer should be able to print text as small as 2 or 3 points if you get the right font. Laser printer toner consists of little plastic particles that are literally melted onto paper, so I would expect the printing would be as durable as the material you print on (test, naturally).

Back in the day there were printer cartridges for printing dense spreadsheets on single sheets that had fonts that small.

I'd expect the tradeoff is the smaller the text, the more light you're going to want to read it by. Also, you might have trouble reading the text if the sheet gets dirty or wet (droplets). Transparency material would at least wipe off.