Is it even technically possible to fight back against a PoW mining attacker with over 51% attack power other than to gain more mining power?

Update:

Apparently, none of the people answering the question can read. PLEASE READ THE POST and its scenarios before answering, because none of the proposed solutions (aside from gandrewstone's) are able to stop this kind of attack.

This is about PoW, not about Bitcoin.

Original Post:

Suppose there is a standard Proof of Work blockchain with a unique hashing protocol not used by any other network.

The blockchain comes under attack by an extremely-rich and well-equipped anonymous entity that has over 51% of the mining power.

The entity is producing blocks that look relatively normal, except that they're censoring transactions from a specific country or producing empty blocks. As far as other miners are concerned, it doesn't hurt them as long as they're not from the country being censored. So any selfish miner would just play along.

But what if the miners collectively to decide to fight back?

Is it technically possible for the honest miners to win without producing more mining equipment?

Options to fight back that wouldn't work

1) Fork the network without changing the protocol?

The attacker would just join the new network

2) Fork the network and change the hashing protocol?

This is a suicidal nuclear option that would piss off every existing miner because now everyone's mining equipment is useless for that network.

3) Block an IP range?

Attacker could just continuously change IP addresses (via VPNs or captured computers across the world). The mining equipment itself is off-network, so they does not need to switch IP addresses. Only the block producer needs to be on the network, and it can constantly change IP addresses.

Options to fight back that would work

Regain 51% mining power

I think the only option is to build more mining equipment and hope the attacker can't acquire mining equipment faster than the honest miners.

Does anyone have other ideas for fighting back against a 51% attacker?