Edit: This doesn't seem to work anymore, does anyone know if there is a step missing?
Since I often use a few items from store worlds, I'm just going to leave this here. Dont want to clog up the game!
You can easily download individual items without downloading the entire world (or set). Here’s how:
1. Open the Sims 3 Launcher.
2. Go to the store website and sign in.
3. Go to the page of the World that contains the item you want to download.
4. Click on the Items tab.
5. Right Click somewhere on the white page border (not on the items) and select View Page Source. A new tab will open. Scroll down a little more than half way on the page. Here you will see the items listed. Find the item you want and look for OFB-SIM3: (You can just search the page for OFB-SIM3: and that will take you to the beginning of the list). Next to that is the item number. For example, the toy machine from Midnight Hollow is number 69433.
6. Write down the numbers of the items you want to download.
7. Copy OFB-SIM3: to the clipboard.
8. Open a new tab.
9. In the address bar, paste OFB-SIM3: and the number you want to download. For the toy machine you would paste OFB-SIM3:69433.
10. Hit enter.
11. The item will now download to the Launcher.
12. Close the Tab. You Must open a new tab for each item you want to download.