The short answer is there is no aftermarket power supply or power brick you can buy for the G3100/E3200. I have tried several options on Amazon without luck.
Your best hope is to try Verizon FiOS support to see if they can replace or send one to you. Although, I personally found more luck going to a Verizon equipment drop-off site (the place Verizon lets you return unwanted equipment) to get a replacement.
FYI Verizon does not stock G3100 or E3200 power supply bricks in their standard retail stores.
If this changes, I’ll update the post.
Other things you may want to know about the G3100 and E3200 Power Adapter
- Verizon changed the plug size and amp requirements for the G3100 and E3200.
- You cannot use the G1100 or G1500 power adapter on the G3100 and E3200.
- The G3100 and E3200 require 12V 3.5A power supply with negative on the outer edge.
- The G3100 and E3200 power supplies are interchangeable.
In my personal experience, the DC plug looks close to but sadly is not quite a 5.5×2.1mm plug.