Most epoxies are based on diglycidylated aromatic nuclei. Ozone cleaves benzene rings as well as all other unsaturated systems. You are eaten if you are limited to common organics.
One hope is to load the epoxy with inorganic filler to blunt ozone's attack by physical blockage. Finely dispersed oxides are a good idea (silica or alumina; fumed silica will tremendously thicken the mix at low loadings). Metallic aluminum dust or paint flake would be even more interesting, as would waste silicon dust from semiconductor sawing. Ozone attack on the filler would give alumina or silica of greater volume than the elements, swelling the attacked surface into a protective cap as the organic degraded. That might be clever.
Have you tried something cheap and easy, like dipping a layer of paraffin wax to block the ozone? Straight paraffin shrinks too much when it solidfies, but it is easy to compound to render it flexible. Just be careful that all components are fully saturated aliphatics.