Hi Alberto,
We use the IP2Location database
http://www.ip2location.com/?rid=744(We're an affiliate, so we get some commission if you use the link above when you buy something. It doesn't cost you anything extra.)
The database is updated regularly and starts from $49 per server per year. The cost goes up depending on how much information you want about the IP address. So for example if you want just country, that's $49. If you want country, and region and city then it's $199 per year. Assuming you're actually doing something with this information it's remarkably cheap.
We also have some code already written to import their database into clarion files (ie a Dict, import routines and so on.) If there was a demand for that we could release it. (hmm - I guess we could release it for free to people who'd bought using the link above...)
Cheers
Bruce