I might suggest moving on/up the vaping ladder a bit, or at least giving it an inexpensive trial or two. You may be pleasantly surprised by newer setups, often you'll get more features, longevity and sometimes a better vape and etc. It can be a bit hard giving up a beloved setup but once replacement materials become harder and harder to find, you may have an easier time trying something else. Maybe a MTL but more adjustable tank setup, or a more recent pod mod system, they have made some advancements and etc., possibly causing them to be cheaper or at least more available than other setups.
I might suggest trying an RTA or RBA if you haven't, that is truly something that for the most part, you won't have to search out parts for other than maybe a tank replacement or two, and some 0-rings and etc.
Best of luck, I was somewhat bewildered by the dizzying array of options when I got here, serious about vaping for the first time. But, I did find following suggestions and trying out some different things to be helpful, and it's nice knowing I can be self-sufficient as a vaper given the way vaping is gong.
Anna