As far as I know, other than trap gun$, the only single-shots currently manufactured, hammerless, are Baikal MP-18's and the Yildiz .410.
No one currently imports the Russian Baikals because of import restrictions resulting from Ukraine activities. The Yildiz is available only through Academy brick and mortar stores. For the money, both are hard to beat for reliability and carry weight. The Yildiz is a knock-off of the old Beretta folding design. Gil