Buy whatever you might need from Lowes or HD and just return the left-overs that you end up not using. I'm sure you'll get the aerator done the first time around.
That faucet can really be made by anyone since there are many knock-offs of brand-name designs. But it won't matter for the aerator.
The other problem with getting standard off the shelf parts is that most of them are chrome, so they'd stick out a good deal visually.
You can be guaranteed (with 100% certainty) that you'll only find chrome samples in-store at Home Depot in the plumbing parts aisle. They'll be able to special order nickel and stainless, otherwise you'll have to go to a specialty shop or buy online.
Is there any part of the original aerator left in that faucet? In other words, is the outside threaded part still there and maybe the previous homeowner simply removed the screen? If so you can do some part swapping. That faucet looks like it should have a hidden aerator anyway, not one protruding from the end.