Nissan altima

My 1996 Altima is leaking oil into the distributor, according to one of the treads this has to do with the distributor seals. I pulled my distributor and found out all 3 seals are broke.
I am triying to buy the seals but even the Nissan dealer only sells two of them.
I can't find the middle one, were the cap before the rotor seats.
Any ideas where can I buy this seal or if silicon might replace it?
I do not want to spend money on a new distributor since mine still works.

Thank you!!
Wingaro