1999 M320 brain replacement

Purchased 'mechanic special' 1999 M320. Listed as needing new brain. Purchased MB brain from eBay to replace old unit. Vehicle towed to dealer for required 'flash' to reset brain. Dealer then informs me the brain unit has a limit of starts after which it will wed to that vehicle identification number. My question is how to purchase a brain part to fix the problem and have the vehicle run again. Can the old brain part not be cleared by the dealer somehow? Can I not purchase a 'remanufactured' brain which has the ability to wed to the vehicle? I am trying to avoid paying the dealer list price for the new brain unit part. Thanks for any guidance.