What about DrBob.Com?
Also, I think it depends on the tone of his writing and blog and such. Yes, he is a professional and trying to do professional work through that website. But is his writing more humorous or whimsical (even at a corny level)? Then something like Dr Batman.com or Dr-Batman.com. Those might even be good (assuming batman is real name) he is a bit of a fan it of the comic genre and it comes out.
Dr in the title might also be really good if he is going to be serious and look at things very analytical like one might expect a Dr to be.
His name, Bob denotes casual, and the last name denotes fun. If he wanted more serious then maybe RobertBatman.com or DrRobertBatman. Com. So I would only go with BobBatman.com if he was looking for casual.
Is the tone something like Ben Nadel at BenNadel.com or like Pinal Dave at SQL Authority or more like Brent Ozar at BrentOzar.com?
I also think it's standard that people know certain websites are all one word., especially when it's someone's name. You hear that often in ads and when people speak about the website.... "just go to Dunkin Donuts dot com, all one word..." and so on. So having the hyphen is not necessary and may confuse some people. Just envision yourself saying it out loud for someone to write it down.... "doctor batman dot com, all one word..." or "doctor dash batman dot com....". See the difference.
People also often capitalize the beginning of the words, as in a Camel-case nomenclature (unless the client is "anti-camel-case" and "pro-snake-case"), as I have done a few times already and people can read it easily as you intended.
I agree that domain names are cheap, get them all if you could.
The primary I would say should be one without a hyphen and DrBatman.com or DrBob.com or DrBobBatman.com if he is looking for serious (like a Doctor) or whimsical (because of the pop-culture reference in his name). The last is my preference, DrBobBatman.com . I like full names for URL.