Our technique works well , but may require a tool to be purchased.
Mostly a big heavy copper for soldering that roofers use ,and a propane torch to heat it.
Simply bend thin 1/8 brass tubing to fit easily in the opening and then solder on brass screening.
You may have to use a hammer to slightly flatten the tubing to be sure the port closes on it.
After the first one they will be a snap to create.
Low temp solder as used for radio repair is fine as even if it has lead , few want to open the port and lick the screen.
The big roofing copper does a proper job in soldering terminals on tinned wiring, after crimping.
The heat it produces can melt the solder at the and NOT pass the heat to the wiring to make it stiff.