Oh, yeah, done nylon webbing/straps like that several times, including adding clip-type straps to my saddlebags, just like yours.
At WallyWorld,
Get a pack of upholstery needles,
And, in the fishing dept, the fine gauge SpiderWire.
And, some Gorilla Superglue.
Figure the placement, cut the straps to length, as necessary. Burn/melt the ends to prevent unravelling.
Superglue a strap in the target position, where it will be sewn. Be quick, this superglue *loves* nylon. Press/hold for about a minute.
I use hammer, pliers, softwood backing, and a thimble (protects fingers). This is some tough stuff, like leather. Hammer/nail the needle thru, use board as backup, pull thru with pliers.
Sew a rectangular border pattern, tie-off on the non-visible backside.
Sew in a filler "X" for more security.
A small dribble of superglue over the non-visible backside stitches will soak in and lock/seal the stitching. Superglue *loves* Spiderwire...