TH, I saw on eBay a double breasted blazer described as WELSH GUARDS' EQUINE BLAZER. It is interesting because it has two columns of four buttons and a much higher neck opening than is customary for civilian double breasted jackets. It looks to me like it could easily be chopped off to kilt / waist length. That would give you a Double Breasted doublet with lapels and a suitable tie space for a cravat or bow.

Here is the link. Even if this one doesn't fit, it might serve as a pattern or example for you:

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

A traditional Navy uniform (dress blue ) jacket might be similar, but again, there's that whole Corps thing going on.