You could use a medical directory such as this one. This one is Mexican and it has filters so you can find an ADHD expert within the clinical psychologists. Contact them.

If you allow me a piece of advice, don’t be cheap with these people. Just because they are used to earn miserably doesn’t mean that it isn’t hard. Living super tightly, stressed because it isn’t enough to save for the future… That’s the reality for many psychotherapists in Mexico —not all, but many. If you can pay them justly because of the euro (obviously considering your needs too), do so, please.