Allowing external internet access through a proxy

Question

Setup: Created VM A with squid proxy installed on an static external IP. Created another VM B. This VM also has its own external static IP.

Now I want to restrict internet access on VM B and all calls from that VM should be proxied to VM A.

I have this setup in GCloud, what would be the best way to make this work.

I have referred a couple of articles on GCloud but most of the examples have this setup within a VPC network and that can be managed through the internal IPs.

Any recommendations on this would be highly appreciated.