Re: does the vision camera HAVE TO be used with the extender
So... like macuser said... technically you can link to the camera directly. But the camera does not broadcast on the Phantom_xxxx SID. It's WiFi net is a hidden ID... that normally you would find by first logging into the extender and browsing through the admin. How to discover the SID otherwise, I don't know. That would be your first problem. There might be more hacker-ish WiFi scanner apps available for an Android phone or your laptop that might be able to sniff out the hidden net. I don't know.
The DJI "extender" basically is a repeater of sorts... so you're rooting around the right tree in thinking to use a temporary one. But, again, the problem will be in the set-up. You'd still need to know the camera's WiFi SID to be able to connect to it even with your repeater. And then you'd need a fairly good repeater admin to be able to set up the subnet, LAN and WLAN correctly to get it all to work.
It'd likely be much easier to find a local DJI retail shop or distributor and testing with one of their extenders temporarily. Then, as an added bonus, if everything works, all you have to do is buy the extender right there and you're back in business.