Domain name registrars (like Dotster.dom) sell domain names. However,
I need to buy blocks of raw IP addresses. Typically, people buy big
blocks from ARIN, and then sell some of the raw IP addresses to ISPs,
who then lease out smaller blocks.

I need a list of at least five such ISPs where I can lease small
blocks of raw IP addresses.

Thanks in advance.

Hello,

Any hosting provider shall be able to sell you some.
ThePlanet.com charges me $1 per ip addresses i use with my servers.

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Hope this helps