Hey Obs!
I got your PM as well, but thought I would post here. We do sell bantam ducklings, but don't sex them nor do we typically sell excess females unless we have tons of extra adult hens (very rare occurrence). When we have ducklings (typically in the bantams just during the Spring), we do not sell less than 10. You might also try Holderread's or Ideal. Holderread's sell several bantam breeds, but again, their minimum is 10 and they don't sell sexed ducklings. Ideal is one of the few that has some bantam breeds they sell as sexed day-olds, but I think they are done for the year as well. If you want ducklings or eggs in the bantam breeds, Spring is the better time to get them. We are going into the time of year when most breeders just sell adult birds, especially in the bantams (closer to Fall though when it is cooler).
As far as breeds, there are a number of types of bantam ducks. The Holderread's have some great pictures on their site of some of the breeds. There are Mini Appleyards/Silver Bantams, Australian Spotteds (three colors), Black and Blue East Indies, Silkies, Mallards (several colors, but Grey and Snowy are the most common), and Mini Overbergs. There are a few others, but they are not common or non-existent in the US. I have bred most of the bantam breeds (all except Silkies). I like them all for various reasons. Most of them tend to be calm and friendly birds. I would do some reading online and go with whichever breed appeals to you. If it were me, I wouldn't necessarily breed them with Calls, but you can certainly house them together. We frequently keep ours together before and after the breeding season with very few problems.
As far as egg laying goes, none of them are known for being particularly good layers compared to other duck breeds like Runners, WH, etc... Most of our bantam hens lay around 75-125 eggs per year. Our best layers far and away are our Mallards. They also tend to lay the largest eggs of our bantam breeds. You can eat the eggs of any of the bantam breeds as well. Now, whether or not you would want to do that is another question all together. You would have to keep a decent number of them to get any significant amount of eggs for eating and most people would probably consider bantam duck breeds too valuable to eat the eggs of. Mallards though are certainly an option for that and a lot of domestic Mallards will lay year round.
Good luck to you. I hope this helps!