Thanks to John Bange and Ken Wilford, it looks like the central
T-fitting/check valve is 281 955 187, and I'll be off to see if this
flummoxes the dealer.

If anyone buys another of the grille/tank/relay combinations from
Neuffer (every once in awhile he'll advertise several of them on
thesamba), either remind him to include the T-fitting or put one on your
parts list.

Thanks,
Walt