If I was you I would not go for custom made insoles. Not only are custom made insoles extremely expensive, I find that they will just support your feet in the position and alignment that is causing your plantar fasciitis. You need insoles that position your feet and correct your biomechanical imbalances! Also I believe that custom made insoles will tend to give your feet too much arch support and will not give your feet any room for them to strengthen on their own.. making you wholly reliant on them, which is far from a good thing.
So ignore the snake oil online telling you that you need custom ones.