The best electrical conductive glue I have tested so far is 2-component silver filled epoxy resin from manufacturer Panacol. It is pretty expensive but allows for repair work otherwise impossible (as for parts that must not be soldered or welded but need a reliable conductive bond). The product Elecolit 325 can be used like a common 2K-Resin curing at room temperature with enough time of 2 hours to apply the sticky mixture. The electrical properties as well as mechanical strength are impressive. See data sheet on:

http://www.panacol.com/images/pdf/el325_gb.pdf

The company supplies samples upon request, but they will charge around USD 50 for handling and shipping a sample of 10 Grams.