Because most of the laws in this country are published to websites as pdf files, it's difficult to search for the specific law that deals with your question. As a business owner here, you must have a lawyer that you use from time to time, ask them for specific reference to the applicable laws(s) and statutes.
True tasers that fire projectiles connected to wires are covered under the main firearms law and are prohibited without a license. In the case of tasers, obtaining a license would require listing a valid reason for doing so if you are not a member of the police or military.
Handheld conductive energy devices - to the best of my knowledge are not prohibited out right but there is a restriction on how powerful such a device can be for civilian ownership.
Cattle prods - low to mid yield devices designed for the purpose of controlling animals are not restricted.
You do not need 500kV to effectively deal with a smallish animal such as a dog. High discharge devices are weapons intended to incapacitate. You merely wish to deter and send scurrying an aggressive animal and not necessarily cause it's heart to explode.
Provided you restrict your use of such a device to animals and provided you don't kill the animal, you should be on sound legal footing on the rare occasion you might need to use a CED. If you use such a device on a person or if your use of such a device results in the death or injury (burns, neurological issues) to a person or animal, you can be found guilty of an offense where by you used excessive force resulting in injury. When choosing a max voltage take into consideration that your intended target is a smaller animal (than a cow) and thus delivering an excessive jolt could bring about an unintended result.
Also remember, electricity doesn't care who it stuns. Zap an attacking dog that is in contact with your dog and both of them will get juiced. Discharge the device when your dog is cowering between your legs and all three of you will get a buzz - and not in a good way.
For practical reasons and to lower the exposure to legal complications, I'd forgo the strong CED's and stick to a low yield true cattle prod (they are available in various strengths) designed for use in prodding something to move along rather than a device intended to turn the lights out of whatever it is used on.
As a foreigner here in the DR, if you need to stand in front of the fiscal or a judge to assert your right to self defense, you need to be able to show that you used a reasonable amount of force to repel an attack and it would be great if the recipient of that applied force is still alive.