According to dealer I must get another catalytic. Is there any after market good one I can buy should I decide to fix the car?
The main dealer will not like to see a third party cat, and might be inclined to blame it without doing any proper tests. You should get an emissions test done, any garage worth their salt should be able to diagnose a duff cat from that. They either work, or don't, or are blocked.
If the MIL is related to lambda sensors, it could be cat, or a sensor, or something as simple as a leak. The key to it is being able to interpret the emissions tests and diagnostic readings from the sensors correctly, otherwise it's just stabbing in the dark.
I've fitted a BM cat on another car before, it lasted a couple of years we had the car, and the next owner run it for a few years until the engine went kaput.
https://www.ebay.co.uk/itm/HONDA-JAZZ-Catalytic-Converter-Exhaust-BM90842H-1-2-2-02-9-08-FITS-EURO-4/311317685938