The odds that you will find a vest in the same fabric are vanishingly small. I think yachtie's suggestions are good. Buff would give it a slightly more countryish and informal look than cream, especially if it were close to tan, which I think is what GBR has in mind. Plus, it's a nice nod to the colors of the US War of Independence, if you like that sort of thing. The first image has more of a buff-tan, while the attachment is more buff-yellow.
Forum member Orgetorix wore a grayish cream odd vest to work. To my eye, it looked good and not too much:http://www.styleforum.net/showpost.p...postcount=1209