Hi there and welcome
Please do not shoot the messenger but there are no replacement bands for the Approach S1.The bands on the Approach S1 are not replaceable. The S2 and onwards all have replacement bands, but they did not have this with the first addition sorry.
Depending on the extent of the damage, you can look at using electrician tape which has a plastic backing which makes it quite strong, as this will fix most of the issues with the S1 strap
If you would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.