Overview
I will inform you the locations of Catnip.
The Bates Motel.
Earlier in the week there is 2 tins of catnip in the Bates Motel. One in The room with the Prostitute and pink light in the hall and the other in the last room upstairs. Im not sure exactly what days but my estimate is Mon-Wed.
Money Shot laundry
Behind the Money Shot there is a dumpster, climb onto it and jump on the wall then walk down the wall towards Fire in The Hole and turn left Jump onto the ledge of Fire in the Hole. Then walk along and jump onto money shot there is alot of usefull stuff most days and you can also get a sawn off shotgun by jumping down from the roof of ♥♥♥♥ Asian. You can acces the other roofs via wires from the telephone poles.
Houses.
Another good way to find em is too go to every house in the game. this should net you a good amount though not every house contains fresh government grade A cat nip.
A week in Paradise
You probably wont be able to do this in one day (Game not a real day) but if you lather rinse and repeat you should get it by thursday AT THE LEAST. =)