I've checked about the entric coated peppermint oil on the net (in Japanese) and IBS.
I don't think entric coated peppermint oil is readily available as a product (the only website I managed to find is the one selling entric coated peppermint oil which is obviously imported from the US, maybe shipment is to be made from the US too as the prices are shown in US$), at least you cannot find it at ordinary pharmacy.
Peppermint oil is available at shops handling herbs and oils.ツ Also some pharmacies are carrying peppermint oil in bottle. (At a pharmacy you can ask for ニ地ニ鍛ニ谷窶禿サ hakka-yu, which means peppermint oil in Japanese).
I'm not sure if entric capsules are easily found, though...
If you need entric coated peppermint oil, I think you should bring them when visiting Japan to be on the safe side.
Some words in Japanese in case you want to find something related to this:
ニ地ニ鍛ニ谷窶禿サ hakkayu (peppermint oil) at pharmacies
ニ馳ニ恥ツーニ蓄ニ停?愴暖ニ棚ニ辰ニ停?ケ pepaaminto oiru (peppermint oil) at herb shops/health food shops
窶卍ー窶馬ツ青ォ chouyousei (entric)
ニ谷ニ致ニ短ニ停?ケ kapuseru (capsule)
窶ーテ溪?「qツ青ォ窶卍ーツ湘?津ウナ嘆 kabinsei chou shoukougun (IBS)
Hope this helps.