For anyone else’s reference, here’s a picture. The superglue seems to have worked for now. Hopefully it holds up.
Thanks for the tip about the polarity, I was sable to hold the casing down by hand with the power on to check which was was correct. it doesn’t take much for the alignment to make the button stick to the side of the front panel, so make sure that’s lined up properly. The spring will want to push the button up and pull the casing apart, so make sure you have a large enough clip on hand, or something heavyish you can place on top of the button afterwards.
Also didn’t realise that the control board was mounted to the panel, so didn’t need to take off all the knobs. Though it was strangely pleasing to clear those circles of dust that had built up over the years.