weapon straps for figures

Foil, paper, sticky notes, medical tape .... any one of these will do the trick.
Cut to size and paint accordingly.

I like to use masking tape.... it seems to do the trick for me plus I feel that it looks like the real texture of a strap.....

Depends on whether the full size straps were webbing or leather. But in 1/35, even webbing is pretty smooth, most masking tapes are a little bit too course in their texture.

I like lead foil, but paper is easier to work with.

Another possibility is to use PVC electrical tape. Remove the adhesive from the back first, methylated spirits is good for this.

Then cut the tape to the required width using a sharp knife.