I was reading in one of my books on French eating and it mentioned their love of mineral water and the fact that they advertise it heavily on t.v. as keeping you regular (the author said that one type had a catchy jingle that repeated the word "eliminate" over and over again, LOL).
Might be something else the IBS-Cers might want to try. I know mineral oil is a laxative, but it also tastes really nasty. This may be a lighter, better tasting option, although I'm sure not a cure for anyone with serious constipation. But it may help some more when used in conjunction with other things, like fiber and probiotics.
I don't know about regular grocery stores, but I have seen it for sale at The Fresh Market, which carries a lot of specialty and imported foods. Might could look at international grocery stores as well.