I'm not into dressing up my dog, but I do use a raincoat on Bailey. It's much easier for me to dry her and it keeps my furniture clean. If the rain is heavier than a drizzle, I put the rain coat on Bailey. She has no issue wearing it and will pee/poop with no problem. Without the raincoat, she will constantly shake her fur as we walk to try and dry herself. With the raincoat on, no shaking.
When we return home, I just take off the little velcro strap that keeps the raincoat on and all I have to do is dry her legs and belly. Her whole head and back are already completely dry. Bailey likes to rub herself onmy walls, couch and carpet when she is wet, so I am very grateful for the doggie raincoat. I much rather have a dry doggie rubbing against my couch.
Have you tried petedge.com for a raincoat? I ordered on from there once, but it was too big for Bailey.