People usually get bees based on the type they want. Italian Carolinian bees or German for example. Most people get bees locally, but some states will allow shipping between states from a licensed beekeeper. In Hawaii, bee packages are not allowed to be shipped in even between islands. Queen bees can be purchased from a certified source, and we get our queens from Kona Queen.
We do have forage all year for bees, so our bees have a larger cluster, but we do still lose them. If the colony is small or has disease problems, they can be raided by stronger colonies and we leave our bees a smaller reserve of honey, they can still be robbed and if it rains a lot, they can still starve.
It is easier to get bees during the swarming season after the honey flow begins. After October the bees kick the drones out and cluster to keep warm for winter. It is when they are most vulnerable to attacks and starvation if they don't have enough food. It is hard to replace a queen in the winter because she needs to be mated to be able to lay eggs and there may not be enough drones around. We had that problem last year. We grafted a queen onto a queenless hive, but it took a couple of months before she had mated with enough drones to start building brood. Bees share everything they have, so when they starve, they will starve together. in colder climates, beekeepers usually have to leave more honey reserves and feed their bees through the winter.
Queens are replaced by the hive, but if the hive is aggressive, you replace the queen with a more docile queen. Aggressive hives do have the advantage of being able to fend off invaders better and they produce more honey. If a hive is unable to requeen, then the hive is in trouble and needs to be requeened in a short time. Queenless hives are more aggressive, they make a lot of honey but they are dying hives.
Happy gardening in Hawaii. Gardens are where people grow.