Almost all highschools and colleges in the U.S. have condoms for free in the health center. I do not know about other cities and states, but New York has it's own condom that is paid for by the city and can be found at many locations
If you are not attending highschool or college and do not live in New York City, then you will have to purchase your own condoms from your local drug store, and might I suggest the cheapest ones you can find and in bulk.Suction cups with hooks:
I purchased these at a hardware store in my neighborhood for $2 in a pack of 5, but I have seen these in certain dollar stores for even cheaper.Sharpie:
These can be found at art, office supply, and hardware stores. The color will depend on the package design of the condom itself. I used the NYC condom which has a white back and a black front, so I used black sharpies for the back and silver metallic for the front.