Since my BIL is a master plumber I just went to the plumbing supply
house and got them to order it. However even they had to be whacked on
the side of the head to get them to order ASTM 2379 S&D (sewer and
drain) rather than schedule 40 which is much heavier and more
expensive. Interestingly Lowes near me (Bucks County PA) carries 6"
S&D fittings and some pipe. Lowes is only about 25% more than the
supply house price.