Square white light solar filter sheets from Thousand Oaks Optical.
This is great news! Once again you can order solar filter sheets made by Thousand Oaks Optical. The solar filter sheets are being sold by Agena Astro at Amazon.com.
Updated 11:56 PM EDT, August 12, 2017 to update links.
Agena Astro is on the approved list of reputable vendors by the American Astronomical Society (AAS). They are the only company I could find selling Thousand Oaks Optical filter sheets at Amazon that is on the AAS list of approved vendors. Don’t buy any eclipse glasses, binoculars, filters, or filter materials from anyone that is not on the approved list. If a vendor is not on the AAS list they could be selling counterfeits that are not safe to use..
These black polymer sheets from Thousand Oaks Optical are visually safe as well as photographically safe. You get a natural, yellow amber looking sun. You can look through these sheets as a hand held eclipse viewer. With this filter material over your camera lens you can safely look through the viewfinder of your camera.
The one catch is the delivery time. These filter sheet sizes are not currently in stock. You will need to choose a delivery method to get the filter material to you in time for the eclipse.
You will need to make a cup shaped cardboard filter housing for the filter material. This article has suggestions on how to do that. The filter housing will hold a circle of filter material that you cut out of the filter sheet. Each filter sheet is like thin aluminum foil so be careful you don’t damage it. When you slide your cup shaped filter holder with filter material over your camera lens, tape it in place so it doesn’t fall or get blown off.
This list with purchase links at Amazon has the size of the material and the date it will be in stock. Prices have been fluctuating, mostly upward.
Amazon Changes Links So Be Careful When You Order
Before you order make sure you are ordering from Agena Astro. Check the “Sold By” line (red arrow). Sometimes a link gets switched to a different company. As I was re-checking the four links for this article before posting the final version, one of the links was switched to a company that is not on the AAS approved vendor list, so I deleted that link. Update, noon August 10. Amazon changed another link so it takes you to a non-approved vendor. I deleted that link too. That means between midnight last night and noon today Amazon changed two links so they take you to non-approved vendors. More about Amazon changing links from safe to unsafe vendors here.
This is one of the links that now takes you to a non-approved vendor. ShipFrog (red arrow) is NOT on the list of AAS approved reputable vendors.
Update, August 12, 11:55 PM EDT. The following links take you to AgenaAstro which is an AAS approved vendor. The links could be changed by Amazon at any time. Check to make sure they still link to AgenaAstro before you order.
Solar filter sheet. 3.75×3.75 inches. In stock August 17. $18.99. Order here.
Solar filter sheet. 8×8 inches. In stock August 17. $47.99. Order here.
This article will tell you how to take pictures using this filter material.
Links
The Great American Eclipse Series
The Great American Eclipse Series  – All of my eclipse articles (more than 20) are listed at this link. Check back for new articles as they appear.
How to Photograph the Sun (and an Eclipse) with a “White Light†Solar Filter
Make or Buy Your Own Inexpensive Solar Filter to Watch and Photograph the Eclipse
Reputable Vendors of Solar Filters  – the American Astronomical Society
Purchase Links
Solar filter sheet. 3.75×3.75 inches. In stock August 17. $18.99. Order here.
Solar filter sheet. 10×10 inches. In stock August 18. $54.99. Order here.