......hard to find !! I got the 6 piece set (possibly the only full set known) in a Chip Chat Auction about a year or two ago.
These chips are pricey - I paid $132.00 EACH for the 6 chips. If I ever come across an extra Dark Gray chip I will let you know. I think there might be a couple of single Gray chips floating around somewhere.
Take care,
"Mr. Roulette"