Yes, air conditioners are pretty much replace only nowadays. You should just be able to get another C&H inverter and just replace that part and keep the indoor unit you have.

https://cooperandhunter.com/

I'm not sure if this apply everywhere, from my experience, once the compressor went kaput replacing it will cost more or only slightly less than the cost of getting a new one. I have no idea why is it the case. Maybe the higher in cost they already factor in the repair cost down the road, and the lower in cost mean it will break often so you will buy often. Capitalism do be like that.

Is it possible for you to find Daikin brand? I have good experience with it, and it last quite a while too. I've used 3 years, cool pretty fast for my living room.

The compressor units are and have always been disposable. But there is more to consider than the entry price. There is the parts and repair availability to consider. The operating costs matter too. A cheap unit is cheap to buy, but may or may not have good support and cost twice as much to run as that more expensive unit. And product support costs money. A lot of money to maintain. Top tier support can make up a a very large part of the cost of that new unit.

I have one daughter that works for a non-profit HVAC consortium designing and managing long term testing of HVAC systems across the US. And then writing research papers about it. She would tell you the Mitsubishi unit is the better and more cost effective unit over the long run. It will last longer, cause you less problems, and be cheaper to run over it's life time. (YMMV for any one random unit).

If you are simply looking for a quick and dirty fix because you are planning to move out in a year or two, then buy cheap and let someone else be on the hook for replacing it.

Get a new unit stand alone and connect it to the existing lines. AC guy will have the charge the lines again for you, but it should be cheaper than that repair quote.

A brand new split system for one room is about $2000 AUD fully installed for a very well known and supported brand here