where to get spares?

Hi I have an 18v cordless garden strimmer made by performance tools approx 6/10 years ago, it still works fine, but I am looking for a spare battery, I am also looking to obtain new spall any idea's? The model no is pwr 18v SGTB or 5GTB. B&Q no longer do it and do not appear to be that interested in after sales.