A standard periscope with mirrors and lens is hard to make.

Submarine Periscope
Submarine Periscope

How about a selfie-stick one with a unused wi-fi enabled cell phone with camera?

All you need is VR goggles from Walmart for $5.00 USD and a wi-fi hot spot or your own hot spot to link the two cell phones. You observe from you web browser pointed at the other cell phones linked IP address. The periscope cell phone is streaming multimedia to the other.

If anyone looks at you funny you just say I'm watching a video. Mind your own business. A partner can stand about 100~300 feet away holding the selfie-stick while you monitor from a comfortable spot. Also that partner (if he can see you) can run security for you just in case someone is about to bother you like the girl in the photo here is being watched by the guy in sunglasses to her left (your right).