Hello,
It sounds like you're looking for a charger for a Line 6 Variax guitar battery, which powers the electronics in those guitars. Although it's possible that someone suggested a Sony A7III camera charger might work, I would recommend caution before using a charger that's not officially specified for the Variax battery, as mismatched voltage or amperage could potentially damage the battery or the guitar.
The Variax batteries are typically designed to be charged using the Line 6 XPS-DI Direct Box and Power Supply or a dedicated charger for Line 6 Variax batteries (depending on your model). These chargers are optimized for the battery type and ensure safe charging.
To find the proper charger, you could try. Official Site
Line 6 official website or support: Sometimes, Line 6 offers replacement chargers or batteries directly through their support channels.
Reverb or eBay: These platforms often have third-party sellers offering new or used Line 6 accessories, including chargers.
Local music shops: While large online stores might be out of stock, a local music store or independent shop may still have the accessories you need.
To answer your question: while it may work, I wouldn't recommend using a Sony A7III charger without verifying compatibility first. The Variax battery and camera batteries may have different voltage and charging specifications, which could cause issues. Stick with the official charger or a third-party charger that is explicitly designed for Variax batteries.
Best Regards
frank