The zip went in my Alpinestars SMX-R boots so I sent them to these people and they put a new, stronger zip in.
http://www.thebootshed.co.uk/It cost £55 for the 2 new zips and a tenner each way P&P.
A whole lot cheaper than forking out for new boots.
The turn-around time was quick (1 week) and the workmanship is excellent.
