In checking the accuracy of my assertion that a good used combination gun could be found at a reasonable price, I consulted eGun, where I was reassured that this was actually the case.

However, I also found an intriguing combination gun which should meet your every need, should you care to spend 4,600 Euros:

http://www.egun.de/market/item.php?id=4103875

This is a Krieghoff Teck boxlock gun in caliber 9.3X74R/ 16-70mm with a full length insert barrel in caliber 7X57R, heavily engraved and with stock carving, in excellent condition, equipped with a Swarovski 3-12X56 scope with illuminated reticle in claw mounts. Additionally an interchangeable barrel set in caliber .243 Winchester/ 16-70mm equipped with a Zeiss 1.5-6X scope in claw mounts.