Hi Glennno,
We had a few bridles wearingdue to Pulley misalignment on some of the Airush Flows and DNA's last year.
I bought a roll of bridle line (25m) in a dinghy racing chandlery shop and we just replace the bridle on customers kites as they wear out for what it cost us in the line.
We don't bother to sew the ends, just tie a bowline and then tie a half hitch on the shank of the knot and use a little bit of electrical heat shrink spaghetti to "sleeve" the tail against the line proper.
It should only cost a few bucks a metre. The Airush SLE's have replaceable sections in their bridle and it is easy to replace the worn parts.
I hope this helps,