Three of my five LFS's sell live brine shrimp. I'd call around all LFS's and ask if they have some. Sometimes they keep a tank of them in the back room and bag them at your request. Hopefully Greece is no exception
I have heard that those brine shrimp hatcherys can be a hassle, especially the hangover one that could clog up with dead brine and affect your water quality. I find it MUCH less of a hassle to find live brine shrimp.
If you find some, here is how I keep them alive. Some people keep them in the refrigerator, but I haven't had luck with that. Instead, I have a half-gallon rectangular jar. I empty the bag into the jar, then fill the rest with fresh water. I place a heavily weighted (use plant weights) airstone to keep the jar aerated. I drop in some vitamins and garlic to gut load them. This method works very well for me and since I buy two large bags of brine I'm good for about two weeks.
I've noticed after two weeks (sometimes one week) that my brine shrimp in the frig have half died off. Some of my fish still eat them, but I have certain fish that ONLY eat live.
I have two of those jars side-by-side. One has live brine shrimp, one has about two hundred snails for my puffers.
If you don't mind frozen brine shrimp then there is a packaged product called Brine Shrimp Plus that has all types of vitamins and such added to the mixture. It's a great option and all of my fish (freshwater, brackish and saltwater) loooooove it ...of course, with the exception of my Bumble Bee Gobies. They spit out anything that isn't live. I think that if it doesn't tickle their mouths when they grab it they assume its dead and spit it out. Crazy, innit?
Don't know if I helped any, but best of luck!