on mine ...
the flap that closes in front of the lens
had a piece of metal that was like a spring catch too
it latched by friction on a little nubby thing like yours.
(it broke off 10+ years ago )
the shutter is rubberized cloth with metal pieces around the slotted shutter holes.
fred lustig ( and his wife ) have the material and a die to cut and make perfect shutters.
if you don't feel like reinventing the wheel, you might consider contacting him ( fred ),
his prices are reasonable .. and he does very good work ( from what i have heard ).
you might be able to find a work-around on graflex.org as well ...