This video helped me upgrade my spouse's HP 15 CS series internal storage - great job! Costco US has a model of this Pavilion (Item 1373575 / Model 15-cs3063cl)* that uses a 256GB M.2 SSD. Unfortunately, it does not include a mounting caddy, hard drive ribbon cable, or screws for a 2.5" drive. I had to research for hours for compatible parts to mount a spare 2.5" SSD inside. HP's replacement parts for these are either too expensive or (in my situation) oddly unavailable from their website. I ended up finding equivalents on eBay which worked perfectly. Hopefully this helps someone:
1) HP Hard Drive Caddy (Part# L19469-001 - as long as a 15-CS model number is listed, you should be fine. Make sure it includes the metal and plastic rails shown in OP's video)
2) SATA HDD Hard Drive Cable HP Pavilion (Part# L23889-001 - as long as a 15-CS model number is listed, you should be fine. You'll have to gently fold the cable as shown in the video, possibly once more depending on the length of the cable.)
3) Mounting screws (two Phillips M3.0x3.0 screws to connect metal part of the caddy to the drive, then 2 Phillips M2.0x4.0 screws to mount it to the motherboard). I resorted to just buying a variety set from Amazon for $7 as I was impatient, but a computer shop might give them for free if you ask.