I don't think that there is a mod for that and I don't think it's possible without Cleo (at least something that comes close to it).
There is a Script from ATP that creates some parking lots (kind of those in GTA4). So you could define those lots, leave a car there and retourn to it later. Only thing is: the car is stored only for one session and won't be saved.
You can find the script here:
scroll down, there is an updated script in the middle of the page. If I'm right, you only have to change the xyz-coordinates, using the coordinates from that point where you want to have your parking lot (what you need to find the coordinates is given in the second link below).
If you want to park some cars for the whole game, use the parking script:
(I would take ATP's script on page 7, bottom of the page)