Roof Slate scribing/cutting tool

Hi all,

I was wondering where you might be able to buy one of these tools (northside dublin/city centre)? Local building merchant didn't have them.
It's the kind that scrapes the slate and you then snap them in two.
It for tegral's truestonePlus brand.

Would B&Q have these?

Thanks

A carbide tipped tile scriber would do it, worked against a straight edge, only cost a few euro.