It is now very time consuming and expensive to make good quality SxS shotguns that have properly regulated barrels. In times past these types of shotguns were the most preferred and gun manufactures had many experienced gunsmiths who learnt the trade while working under their master gunsmiths to make them.
The reason they are not made much now days is that they can not make and sell them in quantity anymore as they have lost their experienced staff and the market is full of cheaper to make shotguns like Auto's, Pump and O/U shotguns that do not require the same hand fitting required and do not need their barrels to be regulated.
Most people are happy to buy a much cheaper O/U or Semi Auto shotgun for the amount of field shooting that they do.
Your best bet like others have mentioned is to try and find a nice, good condition second hand older SxS, some sell for a bargin for what you are getting as most do not understand how good a quality hand fitted SxS is.
Be careful of most of the newer cheaper made ones as they are hit or miss regarding how well they pattern and where they throw their shot, as most do not have both of their barrels shoot to the same point of aim unlike the better made older guns.