My FI and I went shopping to find his wedding day threads, but we couldn't find anything that wasn't a tuxedo or prom-y looking. The idea we have is for him to wear a light gray vest and matching light gray slacks. Our wedding is pretty casual, so neither of us want him in a tux or full suit.
We're thinking something like this:

Any suggestions as to where to look? Chain department stores? Online?
Thanks!