This is one of my favorite hair style in summer.. because summer is HOT!!
And I really never gonna cute my hair to short o(`ω´+)o
It is actually very easy to make the bun, but need practice.
I made this YouTube video about how to do the hair bun,
I hope it helps!! +.(･∀･).+
I don't think you can get the Japanese comb in United States.
Maybe you can try to ask your friends to get it for you.
This name of that comb is おだんごジャストコーム
They may set price differently in different stores, but it won't go over $10.
I will open an online store soon, so if you still cannot find this comb by then,
I will try to get it from Japan and post on my online store. (●´ω`●)