Difficult to find hardware. Do you have a pair laying around? I've struck out with Fastenal Grainger and Bolt Depot, plus some others.
I need 1 pair minimum or 16 max.
Flat head slotted Stainless:
Screw - 1/4 - 20 thread 3/4" length
Barrell - 3/8" O.D. 5/8" length
Kyle, got mine from McMasterCarr. Stainless -- some 316, some 304.
They also come in a T-nut form that I've epoxied into place.
Can't say they have exactly what you show...
Top Notch Fasteners has up to 1/4" bronze slotted FHMS.
And also bronze cup washers to match.
They have regular but no bronze special nuts.
316 T or Sex nuts should be fine with SB.
I guess you photo shows 1/4" MS?
Not much luck. Have struck out with every purveyor! Surprised that particular piece of hardware isn't original!
Would these work?
http://www.mcmaster.com/#barrel-bolts/=x1zcaz
not exactly... There is a taper that fits into the taper of the outboard mounted cleat. Frustrating that this piece of hardware apparently doesn't exist anymore! Thinking on what an alternative would be.
How about this one?
https://www.fastenal.com/products/details/11103588
Wow! One of my clients is a Fastenal rep and I had him check their stock and even he didn't find that! I think it is a match!! Thanks Mike!
(edit - actually he did find that one - it has a 3/4" head, so 1/4" larger than the others on my coamings)