What type of extension cord should I get to use with my laptop?

I live in a condo with a balcony, but there isn't an electrical outlet to use while sitting outside.
I would like to use my Lenovo laptop computer and not use the battery's power.
What type of extension cord should I get?
It does NOT need to be weather-proof, but I assume a regular cord such as one used with a lamp isn't what would be required.

Just get a good one that's three prong and grounded that's the length you need.

Why would a standard extension cable not work
any simple 13 amp domestic cable will do