Just a follow up...
Couldn't find them in the couple of sporting goods stores (which seemed to primarily sell soccer stuff) I visited in Kyoto. I didn't check a department store.
Ended up buying a half dozen or so in the Sport Depot store beside the Rinku Town Outlet Mall outside Osaka. Not knowing what all the models, colours, etc are out there, it seemed to have a decent but not huge selection (eg. It didn't have all the colours and sizes I was looking for). Prices were ok from what I was expecting.