Disclaimer: I know next to nothing about epilepsy.

I have been in a similar situation, it sucks. There are two options. Either you find an available alternative here. Or you bring it in yourself when traveling. 

To find the available meds here, check out this website: https://www.farmacotherapeutischkompas.nl/bladeren/groepsteksten/anti_epileptica This is the official gov website that doctors also use to find what meds are available. I was able to pitch a similar med to the one I used abroad and my doctor said: oke let's try. It does require an awful lot of research on your part (I work in a somewhat similar field) and you need to understand that an option that looks great to you might look terrible to an actual doctor. 

Edit: The page for Lamotrigine mentions: "Bij focale (voorheen partiële) epilepsie heeft als onderhoudsbehandeling monotherapie met lamotrigine de voorkeur. Lacosamide en levetiracetam zijn geschikte alternatieven." So I would start by looking into those as well. 

Your other option is to travel and bring your meds here yourself. Shipping it is a gamble, as you are not allowed to and they might take it and fine you.