The closest thing to PPCo plastic glue is Weldbond.  It is in
a white plastic bottle with blue and red in the label that says,
"It bonds to most anything!"

I have found that to be true.  I base this on how it performs, not
on any knowledge of the chemical structure.  It dries like white glue,
but becomes transparent.  It would not use it to glue a pneumatic to
the base board without testing, as it may be too strong or too weak.

I used it to seal around the top metal valve plate on Ampico secondary
valves.  The nice thing about it is that is can be pulled off almost in
one string if the valve clearance needs to be changed.  It also works
to seal where a nipple goes into wood.

After scouring the lead powder off old elbow fittings I sealed the
interior and exterior with Weldbond and it has been stable.

Weldbond is made in Canada, www.franktross.com tel.: 1-905-940-1107

Bill Chapman - in chilly Palm Springs, Calif.

 [ The MSDS sheet for Weldbond says it is polyvinyl acetate emulsion.
 [ Ref. http://www.uww.edu/adminaffairs/riskmanagement/msds/files/weldbond_universal_adhesive_frank_t_ross_and_sons_12.2.94.pdf 
 [ -- Editor (Robbie)