If the inside bore isn't pitted/rusty/etc, get a rebuild kit. You will have to remove it to replace or rebuild it. New slave cyls. have got expensive from what they used to cost...around $50 from Mazdaspeed IIRC.
Price correction -
NA01-41-920B - RELSE CYL $47.50
FB01-49-460 - INNER PARTS KIT $13.00