What bitcoin wallets support bip32 extended public key export?
Consider to use a hardware wallet: https://bitcoin.org/en/choose-your-wallet.
IMO all of the available hardware wallet do allow to export an xpub.

But watch out (regardless of what wallet you are going to use)!

Even if you private keys are safe when you use public child key derivation, what happens if an attacker compromises your server and replaces the xpub with a extended key controlled by the attacker?

Be careful and read about "Server Hardening".
Also, if you run a VPS or dedicated root server, your server-center operator may have full access to you file-storage.