USB to SCSI adapters typically cost around $50. Also, they usually don't have a DB25 SCSI connector, so you would need an adapter on top that.

I personally have an HP ScanJet IIcx that is a workhorse SCSI scanner. This thing is a tank. For such a scanner I can justify spending the money. But, if your current scanner isn't worth the investment, pick up a USB scanner at CompUSA for $20-$40. I think there was one on sale three weeks ago for $20 after rebates.

USB 1.x and 2.0 cables have the same pinout. You can use 2.0 cable with 1.x devices, so I assume there is little (if any) difference between them.