Hi,
Are you already living in Guanacaste? If so I suggest you ask people around there.
But okay you've asked here so I'll tell you what I know:
Health food shops do not exist in CR, as far as I know, if you're talking about something such as Whole Foods or Sprouts or Trader Joes.
What you find are little stores that sell a few health food items at a high price. The import taxes on stuff is high here, thus the higher prices...
Vitamins and some health food items, herbs, etc are available at what are known as "Macrobiotica" stores. Any good sized town may have one or more of these stores. But out at the beach, all bets are off.
1, Organic meats are not easy to get, but they do exist but you gotta hunt for them, and they may or may not exist in your area. See if you can find someone locally who knows, is my best bet, or look in Facebook for a page pertaining to one of the towns near where you live where you can get to know some of the people or at least ask questions and get answers, locally.
2. It shouldn't be hard to find organic lemons. There are various kinds. We have 2 varieties - mandarino and mecino. They are sometimes orange, not yellow, but they are not limes according to what we've been told. Ours are organic because we grew them and did not use pesticides or herbicides etc ever. But we don't sell them... But if you find someone in your area that has these trees and don't use chemicals on them, chances are they'll sell you some at a fair price.
3. International shipping as you know it, such as Vitacost, Amazon, etc is risky, and expensive. Even if you find some place who'll ship here, chances are it'll get held up at customs and you'll have to go to Puntarenas or San Jose area to stand in line, and pay what is often an exorbitant tax, to get them.
There are services like AeroCasilla (sp?) which offer to get you stuff from amazon but you'll pay like 50% more for each item. It's not very cost effective, though if it's a car part or something you really need sometimes it is cheaper and easier to get it this way than to search for it and buy it here.
There is aliexpress (.com) for some items but really it's all Chinese and it takes up to 2 months to get the stuff, and so it's okay for some stuff but it's not amazon!
4. Water distillers are hard to find but do exist. Be careful if $ is an issue because some of them use a lot of electricity and electricity is not cheap here. I knew a guy who was looking for one that used less elec. and he was having a hard time finding one. I've never seen one here. Your best bet would be to order one from a service like aerocasilla or have someone bring one for you from the states.
Good luck!