lightweight and liquid-tight bottles

Good idea for certain uses — they're cheap and definitely food-safe plastic (I know, I know, many researchers would maintain that there is no such thing)… Thanks for sharing!

Small Nalgene bottles. They have a lab-tested leak-proof seal. We use them for butter, jam, honey, and they work well.

Cheers

US plastics has about any size a hiker could want.

I got a 2 ounce bottle from REI – 0.41 ounce – didn't leak on the one trip I took it on

Something like http://www.rei.com/product/402024/flat-oval-bottle-2-fl-oz but they said that weighs 0.85 ounce, maybe they're conservative or it's different than the one I bought

Ditto on the small Nalgene bottles. A bit heavier than some bottles, but they just don't leak!