Holli - your grocery store should have them! But the checkout people will look at you funny when you check out.
Swiss chard is usually near the cabbages/bok choy/mustard and collard greens. It looks like this:
Leeks are usually near the celery and/or cucumbers where I shop, and they look like this:
Most major grocery stores DO have them, just not in the most visible places (they won't usually be, for example, right next to the broccoli and bell peppers...more likely they'll be near other veggies you haven't tried).