My daily driver was wrecked in its past life, driver rear quarter panel and into the trunk was replaced, and putting a hard top on is a trick, the whole car is bent slightly. This makes having the correct type mounting hardware a must.
You can buy almost the correct metric hex bolts from Ace hardware, but they don't have the shoulder area missing the threads so the bolts can float and be lined up easy.
My last top had the bolts but they were a banged up mess, end threads were worn off. I bought the bolts from Ace, then ground each one down using the old ones as a pattern. Put them into an electric drill, clamping down on the threads, protecting them with a wrap of tin can material. About 5 minutes each with a file and I had made new bolts.
Those bolts are 2 1/2 inches long, and the threaded area is about 3/4 inch, don't remember the thread specification, the bolts that are in the car that mount the front of the top can be taken to the store to get the right thread type.
Good luck with that top...remember if the headliner is sagging, there are lots of options for a different color that the grey, I have vinyl black with the tiny hole pattern circa 60's, and red on another...Chris