Scraps of toilet paper are always found draped on light poles / other swing-able poles. They are white in colour, and are usually very easy to spot. All you need to do to obtain them is simply swing on the pole, and you will be able to collect it.
Now, the game does a pretty good job of providing you with collectibles maps. They are easily purchasable with Overcharge, but I like saving my charge for better weapons. So I went and searched online for an awesome map of all the Toilet Paper.
Here is a link to the map:
which is from the website:
http://segmentnext.com/2014/10/29/sunset-overdrive-scraps-of...But if you still want an in game map for convenience, and don't mind wasting overcharge / have too much of it, you can go to Two Hat Jack, found in any hide out and other locations in the city.
To purchase your own maps, all you have to do is hold
on Two Hat Jack, hit
or
twice, press
, and scroll through the list of maps for each and every collectible.
Below is a video showing you the pricing of all the collectible maps and every single one that is available for purchase.