To the best of my knowledge, there are no new reproduction hardtops being made or sold for C3's. You can find good used hardtops at larger swap meets, Craigslist, Ebay or maybe through some local Corvete clubs.
The best place I've seen for a huge selection of hardtops is Corvettes at Carlisle. You can find them there ranging in condition from needing a complete reconditioning to looking brand new and ready to drop on your car. I found mine on Ebay...it was close by so I could pick it up and not pay shipping charges.
When looking for a hardtop, be aware that some '69s used hardtops with two attaching bolts on the rear deck and later '69s came with three attaching bolts. If your car has two attaching points, you can use a top with three bolts...the center bolt can be removed by drilling out the rivets that attach it to the top.