Hey, its great that you want to help out! i'm sure they will appreciate the effort!
Polo wraps can be bought from any saddlery, so just have a look around and find ones that suit your budget. Coolers are generally used after a horse has been worked and had a hose. Just like wrapping a towel around yourself to help dry and keep you warm! Coolers wick the moisture away so the horse dries quickly and you can put their day rugs back on again. I hope this helps!