You should be able to find a retail copy of Tiger on eBay at a reasonable price.
I live close to an Apple store so I went and asked one of the employees if it was still possible to get a retail version and he said yes, thought it would cost around $40. I called 1-800-apple. and talked to a CSR and she said it would cost $16 plus tax(live in Cali) and shipping. They even logged the serial number of the Ibook under my name for future reference. I received the DVD in four days (they will know if you have a DVD/CD drive by the serial number but make sure to tell them in case. I believe if you have a CD drive it is two CDs
HTH, Rick
OK, Ladies and Gentlemen! Your lucky day! It just so happens that I kept the invoice that came with the disk. I ordered on 5/14/09 and list.