I'm not sure what you bought, or why you didn't post the make/model of the projector which was purchased, but like buying a cheap laptop, and then putting it outside on a permanent basis, it just doesn't make sense.
A proper projector enclosure costs well over $1,000. You could maybe build something yourself for less, but you have both head, cold, and humidity that must be dealt with because projectors simply don't hold up, just like all electronics don't hold up, unless specifically designed for outdoor use.
I have seen very few actual prices on enclosures as they are extremely rare and very typically custom or highly specialized. But, I did find some here...
It's about $2,900 for a small outdoor rated fan cooled model and jumps to $4,000 for a small air conditioned unit.
If it were me, I would find a proper spot for a projector where I could easily install and remove it as necessary. For the money, it makes the most sense and certainly is a far more practical solution unless you are actually doing a very high end installation.