Step 1, Open Parts TM (TM 9-2320-280-24P Vol 1).
Step 2, Hit up the Table of Contents, find that the section I need is 225 (Windshield Assembly, Folddown).
Step 3, Identify part in diagram ( 18 )
Step 4, Reference following parts list to determine P/N / NSN. (PN 12338845, NSN 5340-01-185-7024)
Step 5, Search the internet for the part, hoping for the best availability and wonderful prices.
This is one of my favorite vendors with it listed:
https://www.hummerpartsguy.com/STRAP-WINDSHIELD-FRAME_p_18343.html
(Listed as must-contact for availability. This is the case for all HMMWV parts. They probably have it and at a fair price, but you'll have to call or email or about it due to AM General restrictions.)
Here's a vendor I've never used:
https://hummerpartspro.com/product/amg-12338845-strap-asm-windsheild-hold-down/
Ebay has them for cheap enough, delivered, that you've probably had a lunch this month that was more expensive than a pair of them; however, site rules prohibit me from listing those.
When you do get them, you should just be able to remove the footman loop, slide it on, then reattach the footman loop: no sewing required.
I don't normally break it down to this extent (with some sass laden in there), but I recall that you just recently acquired your HMMWV and you're probably alone in your region regarding HMMWV ownership, so learning the steps on how to look up these parts is really going to be a very great benefit to you!