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I can't help you with information on a mount. But I think you'll find you want to use a "scout scope" otherwise it'll be in the way of the ejection path. And that's likely why the holes are out on the barrel. A scout scope tends to be a lower power magnification but with a really long eye relief that sits out on the barrel so the ejection path is clear. It should be possible to find a Weaver or Picatinny rail with a suitable rounded lower side to allow mounting to the barrel. But it might be listed by the size it fits rather than the model of the rifle. Measure the diameter so you've got something to work with then start looking at suppliers that have different rails. Then you can use regular scope mount rings.