shutters for 240mm Rodenstock Sironar

My electronic Compur Sironar 240mm lens has "died' (a silent death due to the wee electronics 'thingy' hidden away.
i am now in need of a new 'mechanical shutter for my favorite lens but i'm not sure of the thread. if anyone 'out there' can suggest a 'replacement'... I'm all ears (eyes?)

Ken (becoming somewhat more desperate (day by day) now that the 'worst of winter seems to have 'gone')

I have a Sironar 240mm f5.6. It’s the older convertible one with two aperture scales. It’s in a Copal 3.