Parabolic Microphone PVC Parts
1"x3/4"  Bushing #437-131
1"x3/4" Reducing Male Adapter #436-102
3/4" Coupling #429-007
3/4" PVC Plug #449-007
3/4"  90 Degree Elbow (One side inside threaded) #407-00

This page shows the PVC pipe fittings required in detail.

Hardware:

From Home Depot, the following PVC pipe fittings (plumbing dept)

One each:

3/4" PVC Plug #449-007     $0.79
1"x3/4"  Bushing #437-131     $0.64
1"x3/4" Reducing Male Adapter #436-102      $0.93
3/4" Coupling #429-007      $0.24
3/4"  90 Degree Elbow (One side inside threaded) #407-00      $0.67
1 piece 3/4" pipe (you may have to buy a whole 10' length)     $1.99  (Not Shown)