OK, as the "oddwoman-out" here, I do have many yrs of experience with segmentations. First you need no sander..really. On your lathe make a 12 inch disc ( or the limit of your lathe)with sandpaper...take your glue-ups and flatten the bottom..then glue to your segmentation. Now, after that is dry, & if it is real lumpy, use a turning tool to flatten it. (if it is real lumpy, you need more skill glueing up) If not real lumpy, use a nice 3-4 inch wide board, longer than your project is in diameter,apply sticky backed sandpaper, and use it to and sand . You have now spend $2.00. This process has worked for me for decades.
Now that being said..a sander that you wish to buy is a great tool for a shop. If you can afford one, buy one.