In reply to Sandstone Stickman:
OK, so you have traditional monofilament fishing line which is available in 'clear' at heavy breaking strains. It's nylon so stretches to absorb shocks. It's sold in the UK as 'commercial mono' as it's used by commercial fishermen for longline traces. Cheap as chips.
https://www.uk-hooks.com/details.php?selected=214
It is thick though, and may well show up on video, especially if the light catches it.
Alternatively, you could try modern braided line (essentially dyneema) which is like cotton. This is much thinner, but less shock tolerant. Available in all sorts of colours, but is expensive and you can't buy short lengths. It is hard/impossible to find in 150lb breaking strain in the UK, but you could just double/triple up lighter strains. Braid can be unreliable with the odd spool being mysteriously weak in certain brands, but PowerPro is good:-
https://www.veals.co.uk/acatalog/power-pro-braid-1570.html#SID=10
The choice of dark colours and lack of reflectivity might be useful for your project. Give your local tackle shop a call to see what they have if it's open. Braid needs special knots as it's so slippery, but an 8-turn uni knot with a round turn around whatever you're attaching it to should be fine. It also cuts soft things like a cheesewire under tension as it's so thin. Don't get Fireline as it's very thick.