This is what I use to secure the back to the blade. Just common 5-minute epoxy, can be got around town, I know that Woodcraft carries it. I mix up some 50/50 of both parts, and put it in the syringe, and squeeze it into the slot, then place the blade in and measure the blade at the toe and heel and get them even if not.
So, you always wanted to build handsaws...
Making a Handle
Assembling the Saw