Sometimes I make my own film trays from black card stock. So long as the film tray fits in the scan bed and does not interfere with the section of the bed that's used for calibration it should work just fine.
You can look at the design of the native holders for your scanner and determine where the calibration is being done by looking for the gap in the holder through which the calibration is performed (usually at the top) if it coincides with the holders you want to use for any other model then they should function, though maybe they won't have 100% of the same compatibility such as alignment guides or what have you.