If you don't pull much on the upstroke, you might be able to fashion something that would sort of work, but, isn't that pretty much the whole point of being clipped/strapped in.

Find a set of cleated shoes for those boats, I would recommend my specialized tahoes. You can walk all day in these mtb shoes and they work just fine on my roadie commute. If you can't find anything acceptable, go with the clips.