Welcome to the forum! But I should point out that you definitely don't want to get a bike at Walmart as they won't have anything suitable for you, does that mean you'll have to travel to find a bike shop? If so see if there are and shops close by that sell Kona bikes with the Kona Hoss
http://www.konabikes.co.uk/2008/hoss/hoss.php being an excellent ride for you as it's a bike specifically for, what many of the larger cyclists refer to themselves as, Clydesdales.