Well, if the display is tied to the current locale there's not too much that you can do without the source. You need to contact the module developer to get support on this one.
...but assuming that:
1) you cannot contact the developer at the present time,
2) you need to get it right away,
3) you have no problem in displaying always the same currency sign bypassing the locale format completely, and
4) you have the value displayed in a datagrid...
...then and only then you might be able to solve it by editing the ascx, finding the column where the currency value is showed and adding/editing the property DataformatString so that it matches the criteria that you want, ie DataformatString="{0:$ #,#.##}"
I know I know its not advisable as the currency might be showed in several other places where you explictly need the source, as would be the case with textboxes, but its worth a try.
Cheers,