Bias tape is sold in packages near the thread or zippers usually. It is pre-folded and also, it is cut on the bias, so if you are binding curves, like arm holes or neck holes, this is quite beneficial. It is also slightly wider on one side so that you when you top stitch on the shorter side, you will catch the wider side.
You can always make your own the same way you would make binding for a quilt. Or, you can just cut the edge a little bit longer and make a rolled hem.
No need to make it hard on yourself. Most sewing pattern instructions are just guidelines. You can make changes to make it work better for you.
Just jump in and try it with some cheap fabric or something you aren't in love with. Then you can work out the bugs and see if you really like it or not.
Best of luck!