Ouch! Those are the ones that are hardest to come by! I've never actually seen one in the wild. I had to buy my D8 5 PPI online after about a year and half of looking locally and coming up blank.
I know how your feel. Many years ago a Lakside D8 saw of mine was retoothed to 4-1/2 ppi. It saved a bit of time ripping long pieces of ash. The plate was a touch thin and on one hard stroke the plate snapped. Now most of my ripping is done with a Disston D8 at 6 ppi.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)