You can use
bitaddress to derive the public key.
You only need to click on "Wallet Details" button and enter your private key.

If you enter your private key, bitaddress will give you the public key and private key in different formats.

You can also use
iancoleman to generate numerous private key and public key pairs.
Just click on "generate" button. iancoleman will give you all private keys, public keys and addresses generated from a BIP39 seed phrase.
