I would like to avoid storing private keys for signing messages and transactions on my computer. The logical solution would be a hardware wallet like Trezor or Ledger.
The problem is, I was unable to find a hardware wallet that supports importing existing single private keys. When researching this, I only found "solutions" that consisted of moving funds to the new wallet created by the hardware wallet, however this is not possible in this case for several reasons (such as having many different tokens and also DeFi positions on such a wallet, being logged into DApps with that specific address, having a lot of smart contracts owned by the address, being the deployer of NFT contracts which ties the collection access on OpenSea to the wallet, in some cases sharing the key with server applications or with other persons, and other reasons) - essentially I cannot replace the key, I need a way to protect it as it is.
I understand that because the private key was before or still is exposed (being stored on my computer, or on a server, or on somebody else's computer), we cannot achieve the same level of security as we'd get if it had been created on the hardware wallet in the first place, but that's not the goal for me anyway. The goal is to have the best protection which I can provide in my realm of responsibility going forward. If someone else leaks the key, someone hacks a server that has the same key or someone already leaked the key in the past, there is nothing I can do about that, but I want to make sure it's not at risk on my end at least.
Are there any solutions available for this problem? Are there hardware wallets which support importing existing private keys, or maybe other solutions I didn't think of? Please note that I cannot change the way things are set up in terms of which addresses are used or how smart contracts or backend servers are built, all I have control over is what to do with the private keys I am entrusted with.
