Maybe you have done like we did and went first to the big tux chains to see about matching colors. We were trying to match cornflower blue - easy enough right? The Men's Wearhouse selection was hideous in a clownish sort of way. The vest and the tie weren't even the same color or material - Ewww!
An internet search led me to King Tux Rentals. Awesome! Perfect match in a herringbone pattern for cornflower blue! And the herringbone pattern in cornflower is available for the vest, tie, and pocketsquare. They also have it in plain satin - we just opted for herringbone.
While MW had just a handful of colors and patterns - King Tux had lots and lots!
It occured to me that people who don't live close to King Tux might want to buy the vest, tie, and pocketsquare. The tie and pocketsquare are one size fits all and the vests are general-sized (small, medium, large, etc). I think that they are about fifty dollars to buy, which might be close to the rental cost at the big chain stores for those same accessories.
Or just rent the whole thing - it's just $119.99 for everything!