Thanks, everyone. I think I have enough to work on for now. I'll check w/ the seller whether he still has the original parts. Looking briefly online, it looks like the part is 39111-0038 if I had to buy it (them).
Thank you for the other information as well -- I can ask about the stands and also want to see if he knows whether the front was lowered as well (again, not sure if he did the work or if he bought it that way). Just wanting to know what I'm getting into.
Kawasaki is showing their warehouses having the stock links in.... stock. They are sending orders out a day after they get them, so depending on where you live, that'll effect shipping time to your dealership. You'll need two and they are priced at $30.76 each, assuming you're in the US. Given OEM pricing for parts, that's honestly not that bad compared to what I've seen lowering links go for (sold a set made by PSR today for a 2019 GSXR600, was $149 without install)
Oh, and that is the correct P/N that you found as well.