Yes, proprietary plug, your best bet is going to be a replacement universal PSU with interchangeable right-angle tips, like this:looking for an adapter
Along with an adapter plug like this:looking for an adapter
Although, it's still going to stick out 30mm-50mm.
Wouldn't it be easier to just reroute the power cord behind the laptop?
Or move the mouse?
Or just keep searching the internet until you find a replacement universal PSU that has the required right-angle plug.