Amazon offers the 3M Scotch-Weld 2-Part Epoxy Adhesive 1.25-oz. Tube for $17.06. Add it to your cart via Subscribe & Save, and it falls to $16.21. With free shipping, that's the lowest total price we could find by $23. This adhesive sets after one hour.
Update: The price has increased to $17.40 before the above discount, $16.53 after.