I vote with Andy on these one off designs being rather ill advised (except for well heeled racing teams). But since you have one and you haven't indicated in your post that you have broken any proprietary, not generally available parts yet.... I would recommend starting a search to see if you can find a spare for each of the odd parts...and that seatpost would seem to be one of those. It would be a bummer to break something and find that the entire bike is useless for the lack of a small bit part.

On the side (and tongue sightly in cheek), if the SP dies, you might get lucky by looking for an aero frame tube (in the Framebuilders | Suppliers) forum. Some of those tubes look close to the right shape. If it measures out right then $20 for the tube + $15 shipping + $20 for a regular SP to steal the top clamp part from + $60-100 for a shop to make it happen.... well it makes buying a new frame seem like a pretty good deal. You could sell the old frame on Craigs if you do it while the existing SP is still unbroken.

On the otherside; A lot of folks on the Frame Builders forum talk of their efforts in making things of CF. You might be able to build up a new skill and DIY a part for yourself...