What is a good affordable portable wifi antenna?

for what type of device? we aren't psychic...

Asked and answered:

https://uk.answers.yahoo.com/question/index?qid=20...

You have still not clarified if you mean literally an antenna, to connect to an existing WiFi device with an antenna connection, or you want a complete access point client & possibly that with a separate antenna....

Some laptops can work with docking units that have antenna connectors. Or you may be already using some form of external WiFi device with the laptop.

You are just not giving enough information for anyone to give better answers!

Edit re. comment:

You have not even said how it should connect to the laptop.

Be serious... 

I've set up Wifi gear working with multipoint access and anything from local to over sometimes hundreds of metres to several miles.

With _full_ information I can give you examples of suitable equipment - but not from the tiny amount of info you provided.