Where can I find extra 3m strips for door sensors?

I ordered a few door sensors and during installation I messed up for one of them and had to throw away the provided 3m adhesive.

Are they available at Home Depot/Lowes or online to purchase?

The easiest thing to do is get a roll of double sided tape and cut the strips from it.

You can typically find rolls at big box stores like Lowes/Home Depot or online.