Given that DVD/CD drives are now more often external and connected via USB, they do not conflict with your request for an alternative.
I agree that CD-R discs are not ideal, especially after having a couple go bad on me after a few years. But you could instead upgrade to the compatible M-DISC, where M stands for Millennium.
While I don't know if an M-Disc will really hold for a thousand years, or that anyone will care about your data at that time, M-Discs have become much cheaper in the last few years. For example on Amazon, Millenniata 4.7GB M-Disc Write Once and Read Forever, Read 16x/Write 4x Speed, 50 Pack goes today for $124.95. You can also today find Blu-ray M-Discs.
You would have to choose carefully your DVD/CD drive for compatibility with M-Discs. I have found this M-Disc's list of devices that can write, but I cannot vouch for its completeness.
If you wish to go up another notch, you could pass to WORM tape cartridges, but there you are multiplying the price-tag by a factor of 10.
SD WORM cards seem to have gone out of fashion, while Flash-using WORM seems not to exist. So as far as I can see, the options that are left are CD-R, M-Disc or tape.