The material Kelty used on the D4, Tioga, etc. is generically known as "pack cloth," and is about 7-8oz. per square yard, 400-450 denier, and PU coated. It wasn't a ripstop weave, and didn't need to be, since it's fairly heavy.

Something like this: https://www.seattlefabrics.com/60-400-D-Packcloth-Nylon-895--1050-linear-yard_p_48.html

I'd suggest the V46 polyester thread, also from Seattle Fabrics. Most home sewing machines won't handle the V69 well with coated fabrics. "Regular" polyester thread will work, too, with maybe some extra stitching for reinforcement in places.

You could use lighter fabric, though, like the 210d Robic ripstop from Ripstop By The Roll.

Other good sources are:

Outdoor Wilderness Fabrics https://www.owfinc.com/
Quest Outfitters https://www.questoutfitters.com/