RE: Hard drive caddy like YJ221 but for SSD drive (2.5")
Do you already have a caddy for the 3.5 drive? If so, it might be easier to just use it with a 3.5" to 2.5" adapter (so you take the 3.5 to 2.5 adapter and put it in the original caddy). Here is an example at this link, you can find other ones like this that will lineup with the caddy etc. I am not endorsing the one above but just using it as an example that has worked for me.
Another option is to contact Dell Spare Parts at this link