One of the problems with a standard pre-carved fiddle neck for a cbv is that heel block. You have to do some work to take it down to the size you need and the angle you need. I used dowel running from the neck to the tail for extra strength -- I don't think a cigar box can take the stress.
I think all pre-carved ones are pretty much the same in the budget category. There are fancier ones, but not sure that would warrant the expense. You can shop here: https://www.internationalviolin.com/SearchByKeyword.aspx?word=neck for example.
Thanks for the link Dian in Chicago. Lot of interesting stuff there.