Years ago I had white silkies and white leghorn bantams. Like the LF, the leghorns laid pretty much an egg every day, where as the silkies would lay a few per week, when they were in the mood, then go broody and stop laying for months. Generally, the breeds that are kept for production as LF (leghorns, rocks, wyndottes, rhode island reds, etc) are also good as bantams. The bantam breeds the are "eye candy" (silkies, cochins, polish for ex) are not great layers (but wonderful pets).
I would find a breed you like to look at and take whatever eggs they lay as a bonus. If you can find someone local to get them, all the better. Hatchery bantams are a gamble, more than LF, IMO. They are small and more fragile as chicks and who knows how the parents were. A local breeder can give you great advice about how they will fit with your hens and might even have some older ones that are sexable (that's another thing, bantam chicks are almost always sold "straight run", so you will have to deal with the roosters).
Most bantams will get along with non-aggressive LG, some might even "rule the roost", their feistiness more than making up for their size. Old English Game Bantams are notorious for their Napoleon complexes. They are the Chihuahuas of the chicken world, LOL.