Check your local electrical supply houses, most will sell to the public, they are super friendly and knowledgeable, and they can usually get you the best price on anything, except 12/2 romex... lol.
Try playing with the Visual Photometric Tool (link to brief instructions & tool). Since you're at 16' play with adding different output Lithonia IBH or IBG series fixtures.
Search "high bay" in this forum. Lots of good info on light selection and suppliers. Even though the Best Light Fixture sticky starts out with a recommendation for low bay linear lights, there is also a lot of good high bay info there.