Problem with the vatozone recharge is you really have no good idea about how much 134 is in the system; it only measures pressure on one side. Yes, its a cheap/easy temporary fix, but it can potentially do more harm than good if its overfilled. Since you clearly have a leak somewhere, you'll eventually need to locate/fix it anyway, so this isn't an awful idea.
Most of the stuff they sell has the dye in it, so a small can w/ dye could be worth it to locate the leak, then take it in to a shop for a true fix. Then you have the system evacuated, tested, and refilled correctly.