If you’re making homemade sliders or adorable miniature sandwiches for a party, you can buy mini buns from Neldam’s Bakery. mochimunchie made miniature pulled pork sandwiches with them for a party and the guests loved them.
Another option is to use dinner rolls. San Francisco Sourdough makes a good version, available in the bread aisle in local grocery stores (look for the orange label, not the green one), that won’t overpower the flavor of the sandwich you’re making. foodiegrl has successfully used them to make sliders with grass-fed beef and pickled onions.
The best rolls ever are made by Panorama, but they can be tough to get ahold of. Robert Lauriston notes that they sell at many farmers’ markets (check their web site for locations), and suggests you call ahead to see if they could bring you some when they are at your local market. foodiegrl notes that these are the rolls that Myth restaurant uses for their sliders. Just don’t get seduced by the beautifully glossy, eggy dinner rolls ordinarily on sale at the Panorama stand at the farmers’ markets–they have orange rind in them, probably not appropriate for most savory sandwich uses.