Rear calliper Blanking Plug Missing

Hi,
I have stripped down my rear callipers and now putting them back together . However I have lost the blanking bolt.
Attached a pic of the one I need but can’t find a part number for it ( It’s a discovery 1 calliper)
Thought I could use a bleed nipple as a fix but it’s a different thread
Any help would be appreciated

I'm sure someone will have an old caliper or two in their scrap bin that they could take the part off and post you!
My old sets went last year tho.....