Hello Kev,
I replenished my waist-line Herzim strip a couple of years ago.When you take the old off, check that the screws underneath are all tight and if not put some sealant and a little loctite to keep them watertight. When you put on the new herzim warm it up in a bucket of hot water first, makes it more pliable, and easier to insert, I used a wooden spoon to help.I got mine from Jandi, it's a dead match to the original.Haven't done the door yet as I am loath to remove the hinges . If you search Herzim on here you will find some other articles.