Can't you get the batteries at Walmart, Radio Shack, etc...?
I've replaced several watch batteries over the years, it's pretty darn easy depending upon the style of the watch back. Yes, the screw off casebacks to require a tool.
I've got one of this style that I think I got from Amazon for between $10-15.
__________________
Steve
'08 Boxster RS60 Spyder #0099/1960
- never named a car before, but this is Charlotte.
'88 targa
SOLD 2004 - gone but not forgotten