I would suggest putting the chances much higher by the way...

This is an RP, not the actual game where you can run around in the grass over and over again until you get it, so these generally low rates aren't justified. At most we get like, 3-4 tries per route if we're just passing through? And even those tries take awhile.

There are other methods possible too, like asking a Pokemon you encounter if they've seen a so-and-so, or if they've seen anything... Using your Pokemon to ask them of course. Then there's trying to up the chance of encountering a particular one by suggesting it's near.