quick update here: the issue was the bolt diameter. I measured it with my calipers and it was 6.8mm diameter. so, roughly 7mm. All of the bolts I had measured to either 5.8mm or 7.8mm diameter, which translate to M6 or M8 bolts. I guess 7mm is fairly uncommon. Ultimately I was able to find a matching 7mm and it worked well. case closed!
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