You don't say where this is you are. It's not in your profile. Is it a secret?
Have you contacted the people you bought parts from? Have they said parts are back ordered and given you any time frame for their likely delivery?
Was this supplier a BMW Motorcycle dealer or a known after market BMW parts house?
When the order was placed were you under the understanding these parts were in stock?
Your complaint is not unheard of and a lot of parts houses that have otherwise good reputations may on occasion be having problems.
They should send you the parts or refund your money. What did they say when you contacted them?