In the '70s, camping gear ran from "old & traditional" like wool and canvas, to new-fangled materials like nylon an polyethylene weaves.
Scale will affect choices, too. At 1/25, wide bandage tape can look like canvas. Drywall tape (non adhesive) can look like wool after a soaking for 1/48-1/35.
I 1/35, though, one of the best thing to collect are thrift store scarves & handkerchiefs. Silk will give you a nice drape and be thin like synthetic fabrics, even after painting. Cotton & linen handkerchiefs will work, too.
As noted above, thinned white glue (50-50 to 60-40) is your friend. Making a pattern from stiff bond paper first, is also a good idea. Another spiffy thing, especially when using silk is super-thin CA glue. You "draw" this down a seam to set it. Then cut with a brand new #11 or single-edge razor blade.
At really large scales--1/18, 1/16, and larger, you can use self-adhesive fabric tape to actually seem the fabric.