Strimmer (Missing a Part Please Read Entire Post) (Shiregreen S5)

Bosch strimmer - it has a part missing. The little metal washer through which the strimmer string feeds from the spool has been lost and Bosch do not provide replacements for this model without buying an entire new motor - maybe if you're handy you could make one or think of another solution? It works otherwise but without the washer the line just keeps retracting into the spool. Otherwise might be useful for spare parts.