You will have done well if you can actually find a replica, Ive seen original 1s go for £100s! 
Modern Life preservers just dont look the same either! hehe
One question.....why!?!?!
What Price Glory do a nice B-3. I've not seen a commercial repro of the B-4.
aka Stigroadie
AFRA
better by design
"Truth is a shining goddess, always veiled, always distant, never wholly approachable, but worthy of all the devotion of which the human spirit is capable. "
The yellow is only as bright as they would have been when issued. The major difference between B-3 and B-4 is the leather pad on the front of the B-3. You might be able to remove that with little ill effect.
aka Stigroadie
AFRA
better by design
"Truth is a shining goddess, always veiled, always distant, never wholly approachable, but worthy of all the devotion of which the human spirit is capable. "