They are available, free, on a website called archive.org. I had previously purchased at Ebay auction a CD-ROM of what was advertised as sun tables, but the disc was crap and only made my disc drive shudder as though it was going to explode. No joy there.
Today I was looking online at Howard Sun Compass information, and saw an incomplete one for sale on Ebay. Included in the auction was a CD-ROM of the tables (it may have even been the seller who sold the crap copy years ago), and that was where I picked up the title of the book and name of the author.
For too long I had thought that the tables were nothing more than a nondescript government survey office pamphlet. Most people I corresponded with on forums and guestbooks had heard of the tables, but never seen them before.
Alas, the wonder of the internet and Google. I ran a search string using "Davis sun tables" and out churned a number of hits that took me to Amazon and some old book sellers. I did the same back at Ebay and found nothing. Then I added the simple word "download" to my query and found a copy available at the archive site: http://www.archive.org/details/sunstruebearingo00grea
Sometimes, what you are looking for is right under your nose.