Fiskars and Wiss are two companies that make good quality shears that would probably work well for you. A lot of their products are specialized for certain uses, such as tree pruning or metal cutting, but they also make some items for general use.
I have two Fiskars products, and both have been excellent. One that might work for you is the Quick-Release Multi-Shears. They cut through anything up to very light sheet metal and have real comfortable handles. They have a spring between the handles that reduces hand fatigue, so I like them better than scissors. The edge will chip if used on inappropriate materials, but that would not be a problem with leather. They also have a serrated edge on the lower blade, which would help grip your material. Amazon.com sells most of the Fiskars line, so try searching the Tools & Hardware section.
I have never owned a Wiss product, but have heard people speak favorably about them. For a description of the Wiss shears line, go to your favorite search engine.
If you want to buy locally, try a store like Home Depot or a hobby/craft/sewing shop in your town. They might have more suggestions.