If they don't have an AFC screw then they are the OG Kayfun Lite if they have a AFC screw in the bottom or side they are Kayfun Lite Plus. The Kayfun 3.1 was the best IMHO, it had an AFC screw and a bottom catch cup for juice.
These things were cloned by just about every machine shop in China and some were so good that it was very hard to tell the clone base from the authentic. All the parts are mix and match between the various versions of KFL and are quite hard to find these days. Avid Vaper still seems to have a small collection of parts, all of the stuff on Fasttech is long gone and they had literally hundreds Kayfun pages.
Rebuidable Atomizers - Kayfun Upgrades - Avid Vaper
You are coming in really late to the Kayfun game, roll the clock back to 2015 and they were everywhere. Sorry I don't know what the finned top cap is, SoV and most other custom top cap manufacturers are long gone. Wolvesix still has a facebook presence but I have no idea of any stock availability.
There are still a few Kayfun groups around on Facebook. I've been an admin Kayfun Korner for years, it's not very active these days but asking there for parts might put you in touch with someone that has old stuff for sale. Also try the classifieds here or over on VU.
Kayfun Korner
The Kayfun 3.1 was my very first rebuildable and I loved it, but like most vapers we have moved onto bigger and better tanks.
Have you looked through the old Kayfun Lite thread here on ECF? Closed now but there is some great info.
Kayfun LITE - Part 2