My local Wally World sells Ball brand pectin (I use the No Sugar
Needed or Low Sugar variety) for $1.50 a box.

Anyone ever made pectin stock from lemons??? I know it would likely
be costly if you had to go out and buy the lemons just for that use
but, since I use a lot of lemons anyway, I have been saving the shells
in a big bag in the freezer to give it a try. I found two recipes in
two different books. Basically, you puree the shells, add water,
cook, strain the liquid and then reduce the liquid. It can be canned
(or frozen) for later use as well. 2/3 to 1 cup of the stock to 4
cups fruit or fruit juice.