My battery strap was missing the buckle to connect the two straps.
PJ Grady sells a kit for $48.50. I didn’t even investigate NOS. I decided to modify a battery box strap for use in my car. FYI, here’s how to use the stock strap.
I removed the strap mounts from the body. They are bolted to the underbody with 10mm bolts, with the nuts in front of the rear right wheel, and under the car.
I bought this strap kit from Menards. It is one continuous strap meant to wrap around a battery box. 
I cut the strap into two pieces. My mom sewed the ends together, to attach them to the mounts. Thanks mom! New straps mounted, old straps cut off:
Oops. I looped the strap on the wrong side of the mount. Oh well, not perfect, but it works:
All done:
Costs:
NOCO Battery Box Strap Kit, Part No. HM001CS: $2.99 @ Menards
Sewing: Free!