Im gonna geuss that this is for a brand new project. If thats the case and youre going to do your own artwork under plexi, then 24" is a good size since thats a pretty common size for plexi sheets
If you have a cabinet and youre looking to buy a marque, most of the time a size isnt listed, like on EBay. So you would need to search out the dimensions of the original cabinet
For the record, Tempest is 23.75" wide x 10-12" depending on how youve got it secured