Substitute for fresh ham
It might be called a 'picnic roast' (which is a front leg).  If you can't find that, it depends on the recipe (and what's available) for what I'd replace it with.

If it's a slow cooked recipe, I'd use 'boston butt' (which is actually the shoulder; butt means 'widest part'), but if it's fast-cooked, I'd go for  sirloin roast.

And if they don't have any of those, then a loin roast, but it'll be more prone to drying out.