Open flash is very straight forward, and you can just use a bell button switch to fire the circuit, no electronics just find a cheap second hand flash bulb attachment they are next to nothing these days.

I've just been asked about adding flash sync to an early Thornton Pickard roller blind shutter, not feasible for flash bulbs where only open flash could be used (open shutter trip flash, close shutter) but dead easy with electronic flash. Should sync even at 1/90th