USB WIFI stick regular wifi clients can connect to
 

Any computer with a wifi device can connect to any computer with a wifi device through a wifi adsl router, the adsl function being ignored and maybe unused, ie no telephone line.

Is the same functionality available from a portable device that just plugs onto a USB port and has no other power supply and plays the role of the wifi router as above?

I don't know anything but you can do it yourself. Some USB WiFi adapters can be programmed as a master which is how a router works. You can then run hostapd which provides the access point and authentication functionality.

Only got one usb wifi adapter so a new one is needed. What model can act as a master and is of reasonably good specifications (power consumption, bandwidth etc)?

A wifi router by definition should be able to act like a normal wired router.

I don't know if I understand your exact question. Do you mean you want to plug in a usb nic and let your computer act as a router? Or do you mean you have a usb powered router even a wifi hotspot or other wifi device to act like a router? Some wifi hotspots do let users interact and some do not or some have a web based config to allow or not allow guests to interact.

I just want a wifi router that is small and NOT powered by mains electricity, just a little stick you plug into a usb port.

This is for home networking between 2 computers, NOT internet access. So the router function is not essential. Just the ability to act as a wifi master, while the other computer's wifi device will act as the slave and get an IP through DHCP offered by the master.

Actually there are portable or pocket router's that are USB powered. Should be able to google. Will be easier then what I suggested.

There are some mobile phones which you can use as mobile hotspots, i.e. as mobile routers.
I've also got a RAVpower filehub device which does the same thing (and can also be used to re-charge your phone or transfer data from USB connected storage or an SD card) :)

Play Bonny!

:hattip:

You might want to take a look at ad hoc networking.

They call those usb powered routers "travel routers" or pocket router usually.

I bought a gizmo that is meant to use as a usb flash drive nas that was about $10. Worked OK to let apple phone have a usb. It also had a pretty good router function. Hootoo gizmo.

Beginning to find some devices like that. It would be nice if one had a button that disabled the wireless signal but left the router-to-pc connection working, so the reconnect would be instant when the button is pressed again. Anyone seen something like this?