Given that you've got a Showerhead, there's a possibility that your PID is one of the older style with the legacy connections. CH does have the older coils still available for sale on their site:
Introducing the Flat Enail Coil with 5 pin Den Legacy connection. Comes with braided Kevlar sheath, available in 110v or 220v. Works only with Legacy Connection Controllers.
www.cannabishardware.com
For reference, the one on your list is the newer one here:
Flat Enail Coil for DCup and TBucket systems Braided Kevlar Sheath Protects Wires 30mm O.D. Velcro Strap 100w coil 110v Works in North America 220v Works in UK, EU, AU 5 Clockwise Wraps 30 day warranty only applies to customers that have purchased their Enail Controller from Cannabis Hardware...
www.cannabishardware.com
I'd recommend double checking yours and verifying the connection type before placing an order.
I think the power cord is included with the PID so while you might be able to purchase one separately it's generally included with the device. I think it's mainly listed for clarity as some non-North American customers require different plug types.
Depending on the frequency of your usage, a 2nd PID might be something to consider as constantly switching coils can be a pain. It would also facilitate doing back to back hits with your Showerhead as you could heat up both at the same time if that's of any interest. Another thing to keep in mind is that you'll likely need another stand if you're going to use both simultaneously.
You also may not require both the 18mm and 14mm connectors (3234 & 3237) depending on the types of joints you have on your glass.
The carb cap is required, but there are also other cheaper options available both through CH and with other retailers if cost is a concern.
Carb Cap for our American Quartz Bangers. Flat and direction makes this a perfect cap for your banger. Available for 35mm Bangers. NOTE: This Carb Cap also fits the TBucket and Tsunami bangers!
www.cannabishardware.com
XL Glass Bubble Caps for large quartz bangers. Allows superb directional airflow and pushes your concentrates around to increase function.
www.themininail.com
I've only been using concentrates regularly for the last year so I'm still figuring out my preferences and how best to consume, but I personally like to use a separate rig especially if I'm using flower and concentrates on the same day. I find the flavour is affected when I use the same piece for both. There are pluses and minuses to using different sized rigs, but I think a lot of it boils down to personal preference. I've used an 18mm and a 14mm piece and have had excellent results with both, but I mostly use a 14mm for concentrates and an 18mm piece for flower.
A dab tool of some sort will be required to get the material loaded into the Tbucket, but there are tonnes of different options in this regard, you can even make do with some household items that you probably already have.