Suggest he take off his shoes.
@DavidSchwartz's answer is excellent. If, however, he does not want to invest in anything, and your workplace is comfortable with this, he could simply take off his shoes. Very likely, he's building up static because either his chair or his shoes are not grounding as necessary to keep from building up static.
I know it can sound very unprofessional in some domains - and it is - so I don't suggest it unless your workplace is very relaxed and is absolutely fine with him doing just that. For instance, if there are high profile clients going in and out of your office all the time, don't do it. But if you're a kind of back-end tech company who basically sits in a back room all day, this could be an option.