Whats a cheap caseback tool for changing quartz batteries?

[anonymousmoose]

I looked into my watchbox today. All my neglected Seiko watches are not running anymore

Rather than take them to a watchmaker, I want to have a go at changing the batteries myself.

Can anyone link me to an easy to use caseback removal tool? A took with minimum risk of scratching, if possible.

One of my watches has a square case & caseback.