Reddit reviews Honda 95701-08040-00 Bolt Flange (8X40)

Seems like you just need bolts. Studs are the threaded parts coming out of the exhaust port, which the manifold bolts on to.

Those missing bolts are simply to support the exhaust.

https://www.megazip.net/zapchasti-dlya-motocyklov/honda/nvs50-14817/nvs50-today-28719/nvs503sh6-714748/exhaust-muffler-11090325

Looks to me like you want an M8 threaded bolt that is 40mm long, with a flanged head. Somewhere like Coventry fasteners could hook you up.

Or call Honda and ask if they have the following part number:

https://www.amazon.com/Honda-95701-08040-00-Bolt-Flange-8X40/dp/B007JKQ7K6

Don't ride it like that BTW, the manifold wont enjoy supporting the full weight of the exhaust.