This is a fitting you can use to turn a length of PVC pipe (2"), and some mirrors into a periscope.

The mirrors used in this example can be found on Amazon at this link:
https://www.amazon.com/dp/B000RZQI68/ref=cm_sw_su_dp

Instructions are here:
http://www.instructables.com/id/How-to-Make-a-PVC-Periscope/

http://www.instructables.com/id/How-to-Make-a-PVC-Periscope/