I've found by searching, a crusader's thrusting sword seems to fit the part best, they are easy to find via google.
I also found something that could be useful, a medieval belt http://www.mwart.com/xq/ASP.product/pid.1698/qx/medieval-belt.htm
now obviously upon looking at the above link you'll see it's a leather belt with buckles, obviously in the game Altair has a sash, but for costume purposes you could do the belt then wrap a sash over it for the look but you'll know your sword of choice will be secure so that you won't need to re-adjust constantly.
I'm curious to see what you folks find as far as costume designs/designers or otherwise. I think this is a great costume and also see a large market for something like this at events such as the Renaissance fairs and what not.
i'll try to keep up with the forum unfortunately i have a hectic schedule and a busy mind but if someone wouldn't mind emailing me with worth while updates I'd be grateful.