because of the wildly different characteristics of the two drive types, SCSI/Sata bridges are very uncommon and expensive as og said.
this is because, although Parallel to Serial bridges such as IDE to SATA are fairly common and quite cheap, SCSI requires IDs to each device and bus termination. For this reason, it's pretty difficult and therefore expensive to bridge SATA devices onto some sort of SCSI bus then assign IDs and terminate the chain without something going 'tits up' as it were.
Looking at its age, does it have ISA or PCI slots on the motherboard? You'll be hard pushes to find anything ISA that will do it, but provided you have a common PCI slot, there are a large variety of SATA and SATA RAID controllers to choose from.