Sounds like there isn't a standard. I would probably use whatever is convenient and leave a little extra space to be able to fit an adapter if you really want to be able to swap between brands. Min diameter is usually pretty specific for performance, so I would expect most people doing one would have a specific motor in mind for one. Looks like the part on Apogee is designed for Aerotech motors. So if your question is what motors you can use with it exactly as it sits, the answer is "any aerotech 54mm motor".
Another option, that you would want to research before trying.. Use the largest bolt you might need, then drill/tap the smaller closures as needed. The max difference is 1/8" and every closure I've seen would be fine that way. Note that it may be considered a modification to the motor, so it might compromise the certification status. I don't personally think it should as it's outside anything that burns, but I'm not an expert on that and the LSO at any given launch might have a different view.
