Okay, the currency button appears to be hard coded BUT, I think I might have an alternative for you.
If you click on the upper left corner of the sheet, not the cell, but the sheet, you will select ALL cells. You can create a default template that will show the symbol AFTER the number. Of course ALL the numbers will show up this way and you will need to change cells as you need to them to appear later, but you have this option. There is also the possibility to creating different templates for different scenarios. The one I was suggesting would allow you to load a sheet preconfigured to treat ALL cells as though the symbol must appear on the right hand side of the number.
Let me know if that works for you and I will write instructions on how to do that.