Fuel distributor repair

As my MB 300E 1989 was functioning badly, my mechanic discovered that a species of plastic membrane with 6 circles in auto relief, that is in the interior of fuel distributor is with a small perforation in one of those circles, corresponding to one of the injectors.

We don't find this small component to substitute and I don't imagine one of the most expensive parts of the automobile is made unusable because of a component, that me seems to be of very low cost.

The related membrane is sufficiently fragile and must be common its replacement.

Can you help me?