How to store 1kb of data in an NFT (on the actual eth blockchain)

inb4 "that's not a practical use of the blockchain; just use IPFS". This is part of an art project, so please just humor me for a moment. I'm not trying to do this at scale. I just want to make a couple of these and I know they'll be expensive to mint.

I'm having trouble figuring out the mechanics of how to actually store a 1kb file on the blockchain as part of an NFT. There's obviously no file upload field on OpenSea lol... do I have to find a developer to help me create a special kind of smart contract, or is there an existing NFT exchange that would allow me to do this?

If you know of other blockchains that enable this functionality natively, that's cool and I'd love the info, but for this particular project I need the actual file to live on the base layer of either eth or btc. I'm figuring eth is probably the less expensive and complicated of those two options, right? The concept is that I'm storing this tiny file in a way that will definitely be retrievable in 100 yrs so long as at least one eth or btc node survives the apocalypse, so I think that rules out not only the newer chains but also all of eth's layer 2 since we aren't sure which protocols are going to stick. Right?

Also, how would the file be retrieved, exactly? Could anyone retrieve it who can see the NFT listing? Would you need some kind of special software to retrieve it?

Oh... and how much would this cost? I calculated based on a stackexchange thread from 5 yrs ago and current gas prices and came up with $62... which sounds too good to be true...