The Bee

For the past several weeks we have been doing battle with a bee under our pergola, and so far, he (she?) is winning.  
It is a tough little bugger, damn near indestructible.  It has survived direct hits by bug spray, wasp and hornet spray and even a broom. Nothing seems to bother it much - it always flies off, only to return a few minutes later.  
It's just one bug, but it is eating our pergola!
An on-line search revealed that we are dealing with a Carpenter Bee.

They bore holes in wood - they particularly like cedar - and create tunnels to lay their eggs, then plug each hole with pollen to give the larvae something to eat once they hatch. 
Further research confirms what we already knew - they are hard to kill.  The one most recommended solution - about the only one - is

It's a foam you use to fill their holes.
I immediately ordered some, then last night I got an email saying that it is on back-order.