Giving any link or code to a specific product is misleading since the 2009 MacBook Pros, like almost all Apple laptops, could use one of two different clip types. Apple sources it's keyboards from two companies, Darfon and Sunrex, and although they look identical, underneath the key caps they have their own different clip/mechanism designs and these are not interchangeable. The only way to be sure you are getting the right clip or key cap is to visually identify the clip type of your existing keyboard. That is why thebookyard.com show the photos of the different clip types.
There is no industry standard name for the different clips so companies like thebookyard define their own names for each variant. On Apple's service spare parts list they refer to them as type D or S (referring to Darfon or Sunrex) but this is not that helpful since these two companies also redesign their own clips over time, so a Darfon clip for a 2009 MacBook Pro will be different from a Darfon clip on a 2012 MacBook Pro. To uniquely identify the clip design, thebookyard designate a new letter to every new clip variant that Apple uses.
Anyone who is claiming to sell a clip for a 2009 MacBook Pro without allowing you to identify which of the two types it is, is just taking a gamble. Although it is true that within certain geographical areas, one keyboard make is sometimes much more prevalent but it's still a gamble.
Before buying any clip or key cap for your Apple laptop, make sure you visually compare a clip from your existing keyboard to the clip you are buying. Note that each keyboard uses 4-6 different clips for different shape keys (arrow, shift, space, a-z etc) so you need to compare like for like, not necessary exactly the same key but the same type of key i.e. All alphabet, number and punctuation keys use the same standard clip.
I hope this helps explain what is a deceptively complex subject.