Where to buy toiletries?

No matter where you go in Greece you will find such items. Locals need them too. If these items are to be found at the Athens Airport you will find them at the "Last Minute Shop" or "Hellenic Travel Shop". There are mini-markets everywhere in Greece as well as some "super markets", although the latter rarely compare in size and inventory to what we're used to here in the US.

Will you be staying in one location in Athens, or moving around ? Because "pack light" applies more to the need to get on and off trains, buses and planes than to just taking transAtlantic flights. For a one-stop trip, buying stuff there works fine -- but if you're moving every 2 or 3 days, the bottles and jars of stuff you buy there will still weigh you down.
And given the prices in airport stores, I would only buy there for emergency items.

When I say "pack light" it means not having to pack a lot. We will be moving from place to place but driving an SUV around the country from Athens to Delphi to Olympia to Nafplio to Athens. Weight isn't the issue, "things" are. LOL And I'd like to have enough shampoo, body lotion, etc. to last the trip.
Are there "chains" of supermarkets? Any names of shops? I do realize that the Greeks use the same items but I've never seen a store that might carry them.

Thanks for everyone's help.

Many hotels will supply guests with soap, shampoon, body gel, etc. You may want to check with your accommodations to see if they offer them.

When I travel I buy "travel size" toiletries which work fine in addition to any free things from the accommodations.

There are numerous markets and mini-markets in Athens and all over Greece. If you need something you'll probably get them at lower prices than in any airport which tends to rip-off travelers.

As for Walgreens and WalMart . . . thank God they are not in Greece!

I saw racks of sunscreen everywhere (2 weeks ago).

Finding sundries in foreign lands is an educational adventure. Here in the States I am use to local "supermarkets' being one-stop shopping experiences way beyond daily groceries. Finding toothpaste a number of years ago in Prague was a multi-stop shopping experience. I don't recall where we finally found toothpaste for sale but we had a cultural experience of shopping beyond postcards and tourist trinkets experiencing the market place of ordinary living.

Re Walgreens and Walmart:
They may not be in Greece, but Starbucks and MacDonalds are. Ar-rgh!
On the topic: Sunblock is being sold everywhere. Like one of the other posters, I manage with a couple of travel size shampoos for 3.5 weeks. Same for toothpaste.

Re: Walmart/Walgreens et al.

I've seen the Starbucks & McDonald's in Athens. I suppose if you are a local they might be a novelty or an experience but as a American going to Greece or any other foreign country the last thing I'm going to do is go to one of those places. Sorta loses the whole idea of going to another country.

Anyway, as I stated I bring enough carry-on toiletries to supply my for 13 days in Greece. They didn't add much weight or take or much room in one small suitcase. I bring along a regulation-size carry-on backpack for important things that I keep with me at all times. The only time I needed to go to a pharmacy was when my wife came down with a cold and she needed something to help. In addition she wanted some type of lotion which was easy to find.

Just because Greece doesn't have the Big-Box Retailers like in America that doesn't mean they lack the necessities for life . . . it's just smaller, locally-owned, Mom & Pop type businesses. Far more personal, customer-friendly and a lot more fun shopping.