Double Rifles and Drillings have been the provenance of the Europeans and those on other continents for many years. I'm not sure about whether any drillings have been made in America, but I think some double rifles in the traditional side by side configuration have been made at some point in the past.
I've seen some cheaper over/under double rifles at a Gander Mountain a few years ago and didn't pay enough attention to them. Perhaps a cheap(er) over/under rifle might be the way to go if no American gun maker decides to make a double rifle.
Baikal has been making combo rifles and double rifles in Centerfire for awhile, and I've teetered on the verge but think their double rifles are a wee bit overpriced for the fit and finish. I've been sort of impressed with the double barreled Baikal shotguns I've shot in the past, if by nothing else other than their rugged construction, reliable performance and general accuracy. If their double rifle was priced at less than $500 I'd snap one up, but for about $850 + it's not a bargain. The last new .30-06 double Baikal that was on the net but at a semi-local dealer was priced at $1,000.
Maybe a good used one reflecting some depreciation will come on the market in the near future.
I could think of all kinds of interesting double rifle calibers, but as I've mentioned in the previous post, the ready availability (until the past few weeks) of both 7.62 x 39mm and 7.62 x 54r and their relative cheap price compared to similar cartridges with similar performance. In the case of both, they come close or edge out (depending on who you listen to) their American counterparts, and I personally think the 7.62 x 39mm is superior to the 5.56/.223 round in many ways.
Both these Russian surplus rounds are great hunting rounds and there are not many or any modern sporting rifles in these calibers. But lots of cheap ammo.
Likewise, some traditional calibers like .30-30, .30-06, .45-70, .243 and even some high octane handgun rounds like the .44 Magnum, the .357 Magnum and even something like the 10mm would be great choices to have. It'd be really cool to have a Jr. version in .22 L.R. with a full scale gun cut to a 16" barrel and a shorter stock.