'gray' market IPv4

Where is one of these v4 markets that we can buy some IPv4 space from?
I would prefer to have a place where we could see recent transactions, something along the lines of x amount of addresses for y amount of monies.

Google search is failing me for some reason..

- Thanks,

Even if we're happy with our current v4 allocations, I think seeing what sort of rates blocks are going for (even if they're anonymized) would be nice. Prefix length and $ would I think be the relevent items.

Google "buy IPv4 addresses." The first four links are places facilitating sales.