Love my Castelli Perfetto vest...bought it here:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
stretchy: check
bright but not obnoxious: check (I find the orange a touch darker in person)
rear pocket: check
on sale: kind of check (Amazon showing it 19% off)
As for sizing, I am 5'6.5" (when you're under 5'9" my policy is it's ok to count half inches) and weigh 145lbs. Bought a medium and way too small/tight. Large fits well, but I lift weights and don't have a svelte upper body.