I found these...I found an issue (or two) with using the Piezo switches, or at least with the ones I have available. The pulse width on them only appears to be very short, almost not enough for the torch circuit to detect. I find I have to press mine really hard, sometimes several times for them to generate a pulse that is long enough (in terms of duration) for the torch to detect. I'm not sure if there's a way for me to wire something in series with the two switch wires to mitigate this?
I used these switches: Link
Off the back of the above issue, they don't have the same tactile feel as a mechanical switch. I've been looking around for a mechanical magnetic reed switch, however they don't seem to be readily available in push button form around the size needed for this application, at least not that I can find.
Buy IP68 Waterproof Anti-vandal LED On/Off Switch | Oznium
Waterproof Anti-vandal LED Switch, stainless steel housing with IP68 waterproof rating. It's fully submersible and durable. Available from Oznium online.
www.oznium.com
IP68 Waterproof Switch | Stainless Steel Waterproof
The best IP68 Waterproof Stainless Steel Latching On/Off Switch. The Stainless Steel Housing provides is an IP68 waterproof rating. Shop Online from Oznium.
www.oznium.com
The latching one the button stays depressed when circuit is complete. Says it needs a 19mm hole though, probably too big.