Hi All,  Many thanks to all the folks who responded to my request
for Simplex block valve units.

During the course of the process, I was informed that there are two
sizes:  The regular blocks, for the more common 3-tier model, have
round pouches.  The units for the 2-tier model have oval pouches,
and they are narrower than the 3-tier version.

Again, thank you to all who responded, and to the MMDigest for
working tirelessly to keep this fine organization operating.  Don't
forget to make an occasional donation. :-)

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA