That's a PEGASUS contemporary series faucet that is model #856 0111 in CHROME PLATE (lifetime warranty)... your model number would be slightly different... probably just add a BN for brushed nickel. If you look at the mixer valve on the left (single lever valve), I'm betting if you look super close that you will see PEGASUS in really small script writing... let me know.
Home depot sold this brand faucet so you will need to contact the manufacturer and e-mail them a picture of the faucet so they can send you a replacement SPRAY DIVERTER. At the same time, have them send you the instructions on this as I believe the spray diverter is in the mixer on the left... not the spout, but I am not 100% sure on that...
With all that being said, it seems to me that the issue is more likely to be at the mixer cartridge itself
... not just the spray diverter as both the spray and the faucet are involved, you know? I'd disassemble the mixer valve on the left there (shut off water below) and then clean all parts, and pulse hot and cold shutoffs from inside the cabinet to on (towel over mixer) to clear the lines. Reassemble and check your work. It could actually be that you need a new MIXER CARTRIDGE
You can reach the warranty/parts department at: 1-877-580-5682.
If they insist on a model number try using the model number I posted as it is the same faucet... just different finish is all... right? Otherwise, ask if you can e-mail a photo... that should work, too.
Let me know how you make out, OK?