Hi Bob K. Unfortunately I dont know where else that you can get this driver from. To find this one I seached for 3 mode SST 50 driver. No hassle what so ever from the shop I got it from. There is another driver that I have used that is 3 mode 5 amp. In low and med it has a slight buzz coming from it and the modes are not spread as well as this one. Its shorter but a lot larger in diameter.
http://kaidomain.com/product/details.S020121
I used this one here. Again I have only had both drivers for a short period of time so can not report if there going to be reliable or not. What was your intended use and good luck in your search.
https://budgetlightforum.com/t/-/9867