There are various hold items you can use to reduce the encounter rate, such as a Cleanse Tag or Pure Incense. (If the first Pokémon in your team holds it)
In Generation 6, another way of reducing the encounter rate is to use the move Flash, but it only works in caves. In previous generations, Flash only lights up dark caves and does not affect the encounter rate.
So, to answer your question specifically, no. You can not make your own repels.