As you probably know already Oris don't do a leather strap for the DD and I don't know if one of the other straps will fit it so you may need to get a custom strap made owing to Oris using non standard lug sizes. There is a vid of how to remove the pins from the DD on the Friends of Oris site.
More than a few strap makers sell leather straps for Divers Dates. I've got one from Jacob Straps in Spain and a guy in Canada who has a site called Combat Straps sells them as well. There are others, but I don't remember the names offhand. A Google search for Oris Divers Date and Leather should get you pointed in the right direction.
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