I think you’re stuck in never-never land of the Amazon/eBay market places ;-{
While looking for case parts is often what I also end up searching in these market places, you often need to reference the part number on what you want and make sure the seller is not posting other P/N’s which don’t apply.
So let’s review what you need to deal with as its a bit more than you likely think! There are two versions of uppercase shells as there are two different keyboard layouts! US and ISO the keys are different and the sizes of some of the keys are different (the biggest clue is the Return/Enter key) so make sure you’ve ID’d the one you want. Then next is the keycaps! You’ll find the lettering will be laid-out differently for the different languages depending on the country the system is sold [https://support.apple.com/en-us/HT201794|How to identify your Apple keyboard layout by country or region]
In your case I think you’ve been caught by getting the 2010 and older or 2012 and newer uppercase instead of the 2011 version you want. For reference here’s the two likely candidates:
* [https://www.thebookyard.com/product.php?cPath=256_103_250&products_id=7780|MacBook Air 13" Top Case & Keyboard - US, Apple P/N 661-6059]
* [https://www.thebookyard.com/product.php?cPath=256_103_250&products_id=7692|MacBook Air 13" Top Case & Keyboard - UK, Apple P/N B661-6059] Note the ***B*** suffix in the P/N for ISO British.