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.
Non-erasable data: When loading non-erasable data, your files are inserted in a partition of the chip, which is separate from the free memory so that it will not get erased even if formatted. When inserting the peripheral device into the computer, two icons will appear: one is read-only and the other is mass removable memory, which can be used freely. It is possible to load any type of data or file. It is only compatible with Windows.Isn't that what you're looking for? – Vinayak Feb 08 '16 at 07:58