It would help if you told us where you live.
If you live near San Jose California I highly recommend "
http://www.towerbiminis.com/". They can work from your measurements but I would feel better if they had the boat. If you had a Nautique then you could just call them up and say I want one because they have Nautique towers sitting in their shop (they provide biminis to the local Nautique dealer).
Otherwise, look around your area, perhaps visit the local Malibu dealer and find out who they get biminis from.