Do A Google search at Bamboo and Rattan Works, the Company is back East. The prices are very reasonable you should be able to get four bows easy from one piece of Rattan. If My memory is correct seems like the price for a piece of Rattan was around $25.00. When You divide by 4 each Bows cost=$6.25.
The shipping cost might be a little on the high price side thou, do to the extra long length.
Better yet give Dean Torges an E-Mail, Iam sure that He will be more than willing to help you, He has been very generous in answering Questions for Me when I asked....ONE SHOT...