Quoted from s1500:Finding those e-clips has proven to be elusive. They only sell them individually at Menards, but not at all stores.
Bought a box of these last year from Amazon Prime and never looked back:
https://www.amazon.com/Neiko-50455A-Assortment-Treated-Retaining/dp/B000K7GRDW/ref=sr_1_3