Call me crazy and some actually do, but I've had my Vangaurd camera for a couple of years now, have it mounted outside up under the eaves a bit, and have not had any issues at all. I had to lengthen the power cable about 4 feet to get the power adapter inside, but other than that, there is no cover, dome or anything. It's position is open to the West and North weather, which is as bad as you can get considering I live in Michigan. It has done very well with all the rain, snow, sleet and ice (knock on wood!) to be honest, but I will say for the sake of other's peace of mind, I do not recommend it for everyone. But if you live a bit down south, say the midwest, and canmount it up under your eaves so it isn't fully engulfed when it rains, it may just be alright for you.
But if you really value your money, time and effort, and like your Vangaurd, it'd be worth the investment to find a means of covering it. I really like the dome kit used for the Sentinel which I just bought for the wife (she loves watching her birds and other critters up close) but do not think it'd work very good for the Vangaurd by any means as it'd sit down below the bottom half of the dome kit and you would lose viewing area.