Kicad is mentioned regularly.Or that toy, fritzing. Have never seen a good schematic posted from that.
Why don't you just edit the library, clone the part, but make the smd pads bigger on the new clone. Another technique, if there's nothing behind, you can put another heatsink pad in the bottom copper layer, and use several vias to connect/bridge the upper and bottom pads. Also order your boards as 2oz copper.