Hot answers tagged shopping
Short Answer: Yes, you could buy minifig heads at a lego store. Caveats: The heads are part of the "build-a-mini" feature of the lego store. So while you could technically just pick 1 head, you would still be charged for the whole set ($9.99 in USA, I believe). So you may as well pick whole minifigs + 1 accessory + hair/hat. Variety of head, torso, legs and ...
Your brick appears to be trans-neon-green, an extremely rare color for 2x4 bricks. It never appeared in any set and it is only traded between collectors. You would be paying over $50 for a brick like that if you are lucky enough to find it. It would probably be best to pick another color, or another brick-size for your project. Trans-neon-green also comes in ...
I just did a search on all three sites for "2x2 yellow brick." Peeron returned 50 results in a wall-of-text format with no images and I really didn't want to sift through it. But I did and none of them was a standard 2x2 yellow brick. BrickLink returned 16 results, all with individual images of specific items, none of which was a plain yellow 2x2 (but ...
On bricklink, your example, if you input the parts into a wanted list it allows you to find stores that have all (or most) of the parts on the list letting you minimize shipping costs.
There is the Build-A-Mini station where you can build three minifigs (plus one accessory each) for $9.99. That said, some stores will let you buy 15 minifig heads and be done with it. On the other hand, when our local store recently had the ghost pieces, they restricted us to 3 of those per pack of 3 figs.
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