There are many options for what you're looking for. Basically a lot of the sailing high tech ropes use a braided sleeve of say polyester with spectra cores. For instance I believe Spyderline is one such. See also vectran and technora ropes.
The cover makes the spectra rope knot like a regular rope (or paracord) but with much higher strength and less stretch. Spend some time poking about some sailing supply sites. You're looking for what's called double braid (with a core) as opposed to single braid (hollow tube like you get when you pull the core out.)
Personally I'd carry some light single braid spectra rope and some spectra/dyneema fishing line... I have some thats .7mm dia and rated as 200lb test. It takes up next to no space anywhere in a small coil. I just stick it in my personal survival kit.
The big downfall of spectra is easy melting... Like running it over a branch or something and pulling under tension. It'll melt and break unless you have some sort of pulley or slider...