I don't understand why you have to have THIS boa. What's wrong with supporting a good breeder, someone who can tell you what locality they deal with, who the parents are, the history of their breeding program. Why support a petstore that can't deal with mites? I wouldn't put money into any facility that is willing to spread disease via the mite. Mites are linked to IBD. Boas are known for carrying the disease with no signs.
Not only IBD, but many other diseases are transmitted through the mite. It just seems really odd that you MUST have this boa. Are you even set up for a boa yet?
And trust me, quarantine across a room is not a good quarantine. All of your animals will have mites in a few days....