Depends on how much you want to spend. You will either need insulators or DIY blue plastic pipe. Wooden posts insulate but won't last as long as concrete.
Wire spacing for cattle is easy but need lower wires if they have calves.
Energizer as has been said can be bought from Lazada but none of them are really weather proof.
Energizers use about 10W so any cheap solar trickle charger above 10W will do.
Aluminium wire is lighter and rust proof if you can find it.
Have a look around the neighborhood do you see any fences with strips of white shopping bag tied to the wire? If so the local cattle may already be trained to avoid electric fences and so all you need is the posts and the wire.