Jim, in casting about for ideas on how to make the ring, I came up with this. How about one of those things that mountain climbers use to snap their ropes together? I can't remember what they're called now.... Anyway, the really big ones are large enough to get your hand through, and a guy could weld it to the bolt, putting the hinged thingy against the bolt. A zap with the arc would permanently shut the hinged thingy. Don['t know what those things cost, but I suspect one would set you back between 10 and 20 bucks.

On the other hand, making one would be a cinch if you had some 5/16" or 3/8" round stock and an oxy-acetelene welder (arc wouldn't work). Put a couple of short pieces of 1" black pipe in a vise, with about 2 inches between them. Heat up the round stock with the torch and bend the stock around the two pipes and weld it shut. Get a 1/2" NC bolt of the appropriate length and weld the head of the bolt to the new oval ring. Drill a cross hole through the threads at the appropriaate length for the safety hitch pin. You should then have a bolt with a ring on the head, and the inside of the ring should measure about 1" x 4". Sound doable?