Other details about this motor are more important than its dimensions.
How much voltage and current does it take? That will determine how you can control it from Arduino.
Also, knowing what kind of motor is it? Is it actually a rotating motor with an offset weight?
Or is it some sort of "buzzer" kind of device? Some of the "buzzer" devices have built-in drivers
and/or they achieve maximum movement by being resonant at some particular frequency.
If your gadget has a built-in driver or it is resonant, then you cannot control the frequency.
But without knowing more about your "Shaftless Vibration Motor" we would be shooting in the dark.
Oh I apologize, I am new to this and didn't realize that those specifications affected the way you control the motor.
"Free-run speed @ 3V: 14500 rpm
Free-run current @ 3V: 60 mA2
Voltage: 3 V
Vibration amplitude: 0.75 g"
That is all the specification that is listed. How do I figure out if it is resonant or if it has a built in driver?
Perhaps you have a suggestion for a vibration motor that has a controllable frequency? My only requirement would be that it can't be outlandishly huge.