How to replace a coolant reservoir tank cap?

My dad forgot to put the white cap on and now it's lost. Today my check engine light is on and the temperature gauge needle pointed on the red mark 1/4 away from my home. I was scared that my car will break down immediately but I made it home safely. Can I use any bottle cap or something that will fit? If not, how much does it cost to replace one for a 2003 Honda Civic EX?
Added (1). 1/4 mile away from home

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