Really depends upon your budget.
My local store has stuff from $5 (typical Santa/Moses cheapo beards) to $12 for crepe hair to $70 for reusable high quality hand made ones.
Advantages of the cheap beards: they are long enough you can braid them & stuff.
Disadvantages of the cheap beards: they look cheap.
Advantages of crepe hair: take your time & they look fairly good, you can make any length you want.
Disadvantages: 1 shot use (unless you are very crafty & can find a reasonable way to attach it to some form that is reusable).
Advantages of the high quality: looks great & reusable.
Disadvantages: can't modify & price.
Their website is not great but they would take pics of what you are looking for & email them when asked: http://www.costumeavenue.com/
(503) 848-3861