Telesis 8 is used extensively in the film industry to attach all sorts of appliances and prosthetics to actors bodies. It can withstand rigorous environmental conditions for many hours. Properly applied, breast forms will remain firmly attached for 3-5 days. I’ve even worn my forms braless and in the shower with no ill effect. It’s really amazing stuff. It’s not that hard to find either. Just do a search for Telesis 8 or “special effects makeup”.