This is how I make my own sun protection cream for horse use, it should have an SPF of 20 ish (TiO2 has an SPF of 25). The recipe is not tested or certified in any way, you follow it at your own risk and I will not be held responsible for damage to your horse or your shed.
The ingredients are water, titanium dioxide and zinc oxide. TiO2 is used as a whitener in toothpaste and as a food additive, ZnO is the main ingredient of calamine lotion. Both chemicals can be bought off ebay.
The equipment needed is a desert spoon, a funnel and a 250mL squirty bottle to put the product in.
The proces is potentially very messy, especially if you're cacky handed, so its best done in a shed and its best to wear overalls or old clothes.