Over the counter drugs availability

Not purchased, but information is that it is available, but likely not under the Miralax name.

You do need to go specifically to a Pharmacy, not a department or grocery store. Since you know the generic name, it will be easier. Miralax has an electrolyte mix in it, chances are the brands there may have no electrolyte, or obviously their own mix. Look for Macrogol, there is also Laxido and several others.