Short side ones usually get a lot more beat up over the years due to being outside the valve cover and exposed to head gasket leakage and lack of oil seepage. The ones on the inside of the valve cover get oil seepage from the top of the engine and usually are in better condition.
If you are looking for new stock type stuff, VB, Moss or a local shop will likely be your source.
If you are looking for aftermarket premium fastners (ARP) then, VB, Moss, APT, Summit, Jegs and the advertisers here are some likely sources. VB/Moss being the most costly and the discount mail order places the cheapest.
You can usually find used stock stuff with the members of this forum.