A common alternative to expensive fixatives is perfume-free hairspray. A firm-hold hairspray is ideal. With a couple of light coats, hairspray can usually seal an entire painting.
Mix 1/2 cup of ink or dye (the same ink or dye used on the painting) with 1/2 cup of salt, 2 tbsp. of iodine and 1/4 cup of linseed oil to create a very cheap and effective fixative. When you finish mixing, the ink or dye can be applied to almost any surface, and binds very strong.
Transparent paint is another popular alternative to fixative. Because of its intended use as a paint, it binds well to most surfaces and, as long as it is transparent, allows the colors on the canvas, or whatever surface used, to shine through brilliantly.
Clear packing tape has also been used by artists to seal their works. Tape can seal the work off from disturbance from moisture in the air and contact with oily fingers. Packing tape should not be used with oil paintings or other works with a textured finish.
Many fixatives, whether traditional or alternative (such as automobile paint), contain harsh chemicals which make it necessary to apply them outside, so as not to cause lingering fumes or health problems from breathing in the fumes.