I imagine many members here, especially in the UK, would have no idea either!
Can you tell us what the purpose of that component is - just a separate junction box, or the top of a flow sensor, or is it part of the pump?
There is a logo moulded in the broken top. Can you identify it?
Personally I would replace that whole thing with a modern equivalent, rather than try to find a cover!
But you never know, there's a remote chance there is a replacement cover that still survives out there, let's hope someone here can advise
