I've got a handful of headlamps that work great, but the elastic has worn out on the headband. New bands are generally north of $10, which is on par with a (cheap) new whole headlamp! Such inefficiency!

Instead, buy a roll of 1" elastic for about $10, then print as many of these hooks as you need, two per strap.

Cut a ~24 inch section of band (mine at 28 was longer than needed).

Fill the cups in the side of each clip with a bit of superglue, and slightly dampen the ends of the elastic before inserting them fully into the cups.

Give the glue a minute to set, and you've got a new headband!