I have tested it to hold at least 0.5 bar internal overpressure, so it can probably hold against anything you plan on throwing at it!

rubber bellow used: https://rconline.se/produkt/batar/delar-tillbehor-bat/reservdelar-bat/gummibalg-df95-4/ 

push rod: 2-56, with roughly 1.7 mm diameter on the non-threaded part

zip-tie: 2.5mm wide

Printed with PLA, 0.1 mm detail, 6 perimeters