I found this recipe several years ago and have used it ever since.
Ingredients:
2 cups of 3% hydrogen peroxide (the brown bottles at the drug stores)
2 cups of distilled water
1/4 cup Arm & Hammer baking soda
1 oz. unscented shampoo
Directions:
(1) Mix ingredients in large bowl in this order: water, peroxide, baking soda, shampoo.
(2) Stir until baking soda dissolves.
(3) Pour into clean plastic jug (a clean milk jug works well) Don't shake it because it will foam like crazy if you do.
(3) Leave the cap loose since it will 'off gas' for a few days.
(4) Let it sit somewhere inside for several days until the chemical reaction settles down.
(4) Pour into a clean spray bottle (I've used the same old Scent Killer bottle for several years)
You will probably have to buy the distilled water by the gallon so go ahead and buy 2 bottles of peroxide and 2 boxes of baking soda and you can make over 1/2 gallon of scent spray for about $8.00 or so. Once I mix it up it smells just like Scent Killer to me.
Good luck with it.