it matters what you are going to use it for
There's no such thing as a trick bike buddy. A bmx technically is a "trick" bike. So just get a bmx if you want to do tricks.
they are more stunt bikes but if you want to do more jumping on and of you should buy a trial bike
One can buy a custom BMX bike in Las Vegas from a few stores. One can get a BMX custom made from 'Just BMX', 'Bolder BMX', 'Bike World' and 'Vegas Bike Store'.
Go to bike shop or wolyworld and buy a link remover.
Not a sprocket only, but you can buy a 23-tooth freewheel that should fit.