You can search for "Permanent fabric glue" on the net or try walmart or Joannes. You can also use a fusible where you apply heat.
The issue with most permanent fabric glues is they leave a hard spot so it might not be very comfortable on a pair of jeans. The fusibles are a bit more pliable but also feel stiff compared to no glue at all. No glue at all means you would have to sew (most likely by hand)