Is this a request for a new circline fluorescent lamp fixture, or a request where to source a replacement bulb for an existing fixture?
If you are looking for a replacement bulb I have done business with www.topbulb.com (use the 'Visual Bulb ID' button at the bottom of the page to quickly locate the bulb you are looking for). I don't guarantee that they'll have the best price but they have had some oddball parts I've sought out in the past. You will also find some styles may be carried at your local hardware store.
I would not use a fluorescent lamp for saw filing. An LED or incandescent lamp will give a more directional light and make the teeth easier to see. I use cheap reading glasses from the dollar store, they go up to 4x and cost less than $10.