ASN registry?

That seems to be the closest to a complete db, but I noticed it doesn't
necessarily have the same info as ARIN. For example ARIN's listing for
1239 has a lot more details than the RADB entry.

From the responses so far, it seems that it is necessary in some cases to

query ARIN, RIPE, and APNIC to find the info you are looking for.

Ralph Doncaster
principal, IStop.com