S83 wheel repair?

This is my newly acquired S83 rimblow wheel I bought over the weekend. the pics are from my dad. He tells me, an u see in the pics, that the bottow 1/2 of the wheel is missing the rubber(?) seal that goes over the horn ring in the rim. says the top 1/2 is good.

what should we do to fix this? I want it to be done right, since these wheels are hard to come by. could I send this out to a wheel restorer? would they know what to do?