I posted over a year ago on this, not good news I must admit.
I've found a pharmacy that can still get Mexitil but it's no long a guaranteed supply.
I've tried Baclofen and Clonazepam as alternatives but neither worked and both induced horrible side-effects.
I believe that Mexitil has been replaced by new drugs for the treatment of arrythmic heart conditions and this has made the continued production unprofitable.