The Polar S-410 uses the same watch band as all the other S-Series bands so you can replace with any of them. S120, S150, S210, S410, S520, S625, S725. S810 all work fine.
To get the exact replacement you can contact one of the
Polar Authorized Service Centers, and they can send one to you, I seem to remember they are under $15-.
You can also change the watch band style entirely and go with a Velcro style sports band, they are readily available at stores like REI and other sports/ mountain type shops. Take your watch with you to match the width of the original band at the head.