Is it possible to use other brands of coffee filters?
Yes. Well, if the shape matches. I have never found alternatives for paper filters (patent restriction?), but there are clothes and stainless steel versions available.
If you're willing to do a bit of work to save a bit of money, consider folding your own filter out of filter paper. For example:
- I have used very large basket filters in a cone filter in a pinch (they can be really cheap; here's one example for about one penny/cent each). You can fold them in half twice, and they fit fine, or even just jamming the thing in the cone works if you're in a hurry. :)
- Actual non-folded filter paper, such as this half-moon shape, intended for Chemex but would also work in the similar cone shape of the V60.
For completeness, here's some more info in the "shape" topic:
There are three primary "cone" filter shapes, with examples from Amazon and other outlets:
- Melitta style (available in sizes including "#2" (most common), "#4", and "#6"); these are passable in a pinch but really don't fit well.
- Chemex style; these tend to be larger, thicker, and more expensive; they produce a slightly different filtration. These will basically work in a V60 cone (but not the other way around: DO NOT consider using V60 filters in a Chemex!)
- V60 style (available in sizes including "01", "02" (most common), and "03"); As @Eric states in his answer, I haven't found a "generic" brand of this shape of paper filters.