Staephj1,
Yeah, that's what I hoped too, but I tried that during our last holiday in Ireland (plenty of opportunity to test waterproofness), and it didn't work for more than a few hours.
I think that movement of the foot, combined with a always somewhat damp from sweat environment isn't the best for adhesion of tape.

But perhaps a combined attack plan of filling the holes AND using tape will give good results.

It looks as if there are no off the shelve shoes like the ones I'm looking for.
I think it's DIY time!

Thanks people!