Here is Gabe's Halloween outfit. I shamelessly copied it from here. Although, I have to admit, I think mine is MUCH cuter--and functional too! I was lucky enough to have a boy's vest pattern on hand, and I just sewed it on to a plain white shirt I bought at walmart. For the tie, I used this site as a guide, but I didn't have enough of fabric to follow the tie exactly so I improvised, and I think it turned out alright.
I think I paid about $5 for Gabe's shirt vest, and it was fairly easy to make. Super cheap and super cute for a super cute little boy!