I use the Logitech G600 mouse. It has 12 number buttons on the side and a g-shift clicker (it has 3 clicks, left, right, and g-shift). The g shift acts like a control or shift or alt key and causes a number button to perform an alternate function. I highly recommend this mouse as it has made my swtor game so very much easier.
My top row is regular numbers, the second row is g-shift + numbers and the third row is shift key+numbers.
It may take practice to get used to it but it is definitely worth it.