I haven't tried this yet but maybe it'll work for you...
You need a measuring cup, tablespoon, funnel, and spray bottle.
8 ounces/237 ml hydrogen peroxide 3% (this can be found in a brown bottle in the first aid aisle of most pharmacies or stores)
3 tablespoons/14.29 grams of baking soda
1 drop of liquid hand dish washing soap
Mix all ingredients into the spray bottle and use within 20 minutes. Do not attempt to store the leftover solution. because it will leak out of the bottle. The mixture only works if you use it immediately, because the cleaning byproducts are active for only a short time period. You should see the stain lift and disappear within 5-10 minutes. Once the mattress dries, if a baking soda film remains, then simply wipe or vacuum it off. Reports I read also indicate this method works well for pet urine stains, but I have not tested it yet in this capacity.
People will forget what you said, people will forget what you did, but people will
never forget how you made them feel.