If the fork takes a JIS crown race, I think it's still very likely the rest of the headset needs to be ISO. If not, because of the headtube's diameter, you'll be stuck with JIS headsets. Also, assuming the headtube diameter is ISO, I think you could make the ISO crown race fit the JIS fork, if not by using a dremel, sandpaper, etc., I think there's a Park tool that will do it (if it were me, I'd probably use a dremel, sandpaper, etc). Maybe another bike shop would have some ideas on that. Here's a link to the Park tool website, check out the chart at the bottom regarding the difference in headtube diameter between JIS and ISO (Euro). http://www.parktool.com/repair/readhowto.asp?id=68

Have a shop use calipers to determine what your frame takes, both for the crown race and the headtube cups (I probably wouldn't go to the same shop you went to earlier ). Let us know how it comes out-

edit: actually, even if the frame's headtube has the JIS inside diameter, you could probably have it reamed to fit an ISO headset-