Rocketman Kevlar Braided Shock cords are the most popular in Low, Mid, and High Powered Rocketry.
Rocketman Flame Shields
Rocketman's Recovery Harnesses
Sold by the foot All shock cords are Kevlar. A general rule of thumb is for the shock cord to be at least 3 x the length of the rocket. Longer is
Kevlar / Shock Cords
50~1800Lb Black Kevlar Line Braided Cords – Emmakites
1500 lb test strength braided cord (not tubular, but it does have a hollow core). Recommended for high-power rockets. Pricing is per foot.
Kevlar Cord 1500#
Parts for Rockets - Shock Cords - Kevlar - Elastic - Nylon - Page
Weather Balloon Y-Harness and Shock Cord
Peak of Flight Newsletter : Apogee Rockets, Model Rocketry
5/8″ and 1.25″ Tubular Nylon Shock Cords
Shock Cord Alternatives Rocketry Forum - Model Rocketry Forums
Rocketman's Braided Kevlar & Nylon Shock Cords
Black Braided Kevlar String 50lb 1000ft Fishing Assist Line High Strength Tensile Heat Resistant for Paracord Cord Ultralight Tactical Survival Rope
50~1800Lb Black Kevlar Line Braided Cords – Emmakites