Calogic LLC makes a line of high-speed DMOS analog switches (really MOSFETs) that seem quite suitable for use in a project like this one. The packaging is also a SOT-143,
Neither DigiKey nor Mouser carry their products. They do have a distributor link on their website, and some of them do sell suitable devices in "small" (less than 2500 unit) quantities. The prices I saw are about 6x that of Mouser's price for the BSS83, but at least there is more than just one device available.