I haven't seen these in leathers, nor have I seen any other aquatimers sporting leather straps.
I do however remember reading that there was an old strap maker that would do this, but the limitation comes with having the IWC lug system stay in place. I think the strapmaker gutted a lug system out of a rubber strap, and "fused" the leather and the metal somehow to make the lug system work with the leather. It was a long time since I read this so I don't have the link.
Also, the older aquatimers used to have a nylon strap "adapter" which pretty much extended the lugs outward by one bracelet link. At the end of the link there was an attachment so that you could loop your nylon strap through. I don't see those too often now either, but they pop up once in a while (search eBay for full sets of the older aquatimer).
Good luck though, if you find something let us know!