temporary body work

If it's just a year or two until you fix it properly, there's a couple of ways I would go. The cheapest and easiest way is to keep it in a garage or use a car cover to keep the water out of the trunk. If that isn't possible, or, you want to actually work on the leak, you need to figure out where the leak is exactly. If it's the seal on the glass, you need to pull that glass and gasket, repair the opening, and re-install the glass with a new or good gasket. If it's just leaking at that hole, I'd sand blast it, paint it with POR 15, and bondo the hole. Rattle can paint the patch and call it a day......or a year or two.