I’ve been using Chinagraph pencils for about 28 years now.
i switched to a type of wax pencil which may still be same name, ill check at work. anyway, reason for the chnage was to get away from the paper-peel type charpen system the chinagraphs have and opt for the more traditional pencil sharpener one.
i think i either bought my last batch via amazon or an online craft shop. I buy them in boxes of say ten at a time.
I have Black, white, blue, green. so about 40 pencils in total and last some time if stored properly.