You know that nearly any hood type encloser can become vented by introducing some holes? Get whatever is going to fit best for you and melt some holes in it. I used a flame and about a 1/4 in. pipe - heat it up, and use it to pierce the plastic. It stinks, but drills tend to split and splinter plastic.
I use clear plastic cups that I melted a series of holes into. Take a look at the clone chamber of my grow and you can see what I mean.
High humidity, with fresh air exchange.
I keep my clones covered like this for the first week - Don't touch 'em at all.