Bulk Flour

Since my home is a part-time gluten-free and lactose-free environment, and since I love to bake, I am frequently looking for stores that sell non-wheat/non-gluten flours in bulk (more than 2 lbs at a time). Most stores rarely have any decent selection; in fact, the store I would think would have the best selection (considering the number of bulk bins they have filled) actually doesn't.
In Ohio, my mother has a bulk food store in Amish country, and she often loads up on stuff for me before coming for a visit -- and sometimes she even mails it to me (of course, once when she did I got a call from the Post Office regarding a package leaking white powder...) -- it can actually be cheaper for her to purchase and mail it than for me to buy it myself, which is amazing, considering she ships around 5 pounds at a time -- or more.
I've been in the Pioneer Valley for about 6 months now, and this is all I've discovered:

Oat Flour: Maple Farm Foods (Hadley), $1.89/lb (recently went up)
Rice Flour: Maple Farm Foods, $1.89/lb (recently went up)
Brown Rice Flour: Whole Foods (Hadley), $1.99/lb (organic)
Corn Masa Flour: Maple Farm Foods, $3.49/4.4lb bag

You can find spelt flour at Whole Foods, but I don't know the price, since I can't use it. And you can purchase rye flour in nearly every well-stocked grocery in ~5lb bags.
Also, Ocean State Job Lot in Palmer often has Bob's Red Mill flours at prices a little bit cheaper than the regular stores (but there again, small bags).

Finding this kind of information online can be difficult, so if you, too, are a gluten-free baker and know of other places in the area where such flours might be bought in bulk (or where the grains might be ground into flour), please add a comment!
What I'm looking for:
Corn starch
Soy flour
(Tapioca flour)
(Bean flour)