Square D has a class 9006 L100/300 series rated for 20 amp continuous (page 21-34, digest 175) but you are going to pay for it. Other manufacturers have similar but I don't have current catalogues. As far as size goes I would go for the small switch (less damage to the cabinet over time) to a relay, it may be about similar in bulk. I am glad we don't have that requirement.
