Go to the Radio Shack website and search for ferrite core.
Snap Choke Core - RadioShack.com for direct link to ferrite core
It is listed as Model: 273-069 | Catalog #: 273-069 Snap Choke Core Price: $2.89
When you locate the item on Radio Shack's website you can either order, or on the right side above "add to cart", you can click "In-Store" and you can enter your zip code and how many miles you want to search from your zip. It will tell you if they are in stock at that store. There were 10 stores, near my zip code, that had them in stock.
When you check your zip code, you may notice, that when you order on the website, there is free shipping for in-store pick-up.
BTW... Another thing I noticed is even with the ferrite core, that if the volume is turned down on my droid, the static returns. I turn the radio volume down (so I don't get blasted away), turn the Droid volume all the way up, and the static goes away. I can then turn the radio volume up to the listening level that I want and no static. I can play my radio with the volume all the way up, if I want to, and I get no static.
Hope that helps...