If you find that Oklahoma curb cut is too costly, go get the saw you used originally and make a second cut all around the outside of the first cut, about two to three inches. Then with a twenty pound sledge, pound down on the "slot" and break it out. You can then form up to repair and narrow the slot with quick-set. Remove the form and then fill the final crack with the expanding foam as recommended. When it is dry, use a hand saw to cut the protruding foam off flush to the floor.
The sledge will not be easy, but it will be cheap.