So it does not matter whether it is running on battery or plugged in? There are several things that can cause the machine to suddenly die so how much do you trust the shop that diagnosed it? That is an expensive problem so it would be a shame to pay for additional parts & repair if that is not actually the problem.
Anyway, if you are confident that the shop is correct then you may want to contact ASUS to see if they will repair it for a fee. Otherwise you might need to find a donor motherboard on Ebay. It won't be cheap though. I think you're unlikely to find separate chips for sale since swapping them is beyond the abilities of most people. You'd need a hot air rework station.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…
