There are a lot of good comments here. I'd like to make a reply to some of them.
I, also, live in an area where it's difficult to find the tatting needles. If I want to purchase actual tatting needles I have to drive approximately 75 miles to a small town. And, I only have one choice of whose needles to purchase.
While it's true that doll needles are not the same size from one end to the other, they are fairly close. Yes, you do need to tat looser and yes, you do need to use a larger thread. The idea behind using a doll needle (or any needle besides one designed specifically for tatting) is that at least you'll be able to tat. No, you won't have an accurate gauge but, since most tatted things are not gauged, there's no worry.
As for using other types of needles and using a protectant so that you don't poke yourself, trying using my suggestion in my articles of sanding the point down to a round shape (using sand paper). It'll make your tatting more enjoyable.
Thanks for your comments and I'm going to go check out the web site listed here in the replies.