Lopis, you're right. Forward planning has never been my strong suit, and backward planning doesn't seem to work for me. There are some smart people in the world who can predict demand. Not me!
And, about twenty minutes ago, I ran out of large Klein bottles. It'll be September before I can get more, what with shortages of borosilicate glass.
[1] https://www.youtube.com/watch?v=-k3mVnRlQLU