I am new to this topic and I am new to this forum too.
I have a 70s Holden with the factory AC condenser made from copper/brass. I am going to retrofit new A/C lines, compressor, evaporator, filter and so on. Going to re-use the copper/brass condenser because it is a better and durable material.
The problem I have is, it has two barb fittings from factory. See picture below.

The AC person wants to convert this to a O ring style connection by welding 1/2" thread, R134 flare copper fitting, so that an aluminum hose with O ring can be fitted with threaded fitting.
He wants me to find something like this, but in copper. (he couldn't find any with his local suppliers)

Can someone please help me find one to buy online or give some advice how to get this sorted?
I am not sure whether this is the correct type of connector, or whether there is a better way to do this.
TIA guys