Herb, Herb, Herb...I love you! The link for the LB3499 led me to a gentleman in NC that not only has the seal, but also the bumper. So, I have ordered the parts (including a new "O" ring kit).Hmmmmmmmm...............are you OK,Bill? Sure?
You can get a BC178 Here: https://www.alibaba.com/showroom/new-bc178.html
And A LB3499 seal here: https://duckduckgo.com/?q=lb3499+seal&t=ffnt&ia=web
And Senco sn325 parts here: https://duckduckgo.com/?q=senco+sn325+framing+nailer&t=ffnt&ia=web
Here is the link to the place where I found the parts.great...
now do you have links for the rest of the world???
Sounds like Monty Python's Dead Parrot Skit.Dan - the owner of that pet shop sounds a lot like Basil Fawlty - let's see who's stumped.
Good Work ,Igor.:grin::grin::grin::grin::grin::grin::grin::grin::grin::grin: