I've found several that adapt 2.5" IDE to 3.5" SCSI (normal 50-pin connector, not the Powerbook's 40-pin), which are somewhat confusingly listed as just 2.5" adapters. I've found none that do 2.5" IDE to 2.5" SCSI though. They exist of course, but the only known source is the larger 2.5" SCSI drives which are rare and cost as much or more than the CF adapter.
If you do know another source though, by all means tell us.