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

Go to a dealer and get an OEM cap - it needs to hold a certain pressure.

Talk to a local car parts shop, give them all the details of your car and they will be able to get you the right cap. No a bottle cap isn't suitable. Cost wise somewhere between $7-$40 dollars depending on the type of cap. If you go to a Honda dealer it could possibly be even more

If your talking about the cap on the opaque colored plastic overflow bottle rather than the radiator cap itself you have other issues, As in no way will this trigger a check engine light or result in your engine over heating, as this cap serves about the same purpose as the cap on your windshield washer fluid reservoir, keep dirt out and fluid in, Nothing else, Now the fact it was removed by forgetful dad makes me wonder if he topped off said reservoir, in which case suggests an underlying problem may have existed to cause an overheating problem in the first place, If you'd like a suggestion from a 30+ year veteran mechanic, take your vehicle to a qualified mechanic, preferably by way of tow truck as to not further damage your engine more than already done, Although expensive not as expensive as a new car or engine

This is not a commonly replaced part, but a Honda dealer should be able to get one for you. (I noticed a crack in mine; the Infiniti store charged me $11 for a replacement.)