My 2009 Mazda6 has an apparent security system issue. The alarm beeps continually when the door is opened as if the key is left in the ignition. The key fob will not lock/unlock the doors as a result. The doors can be locked/unlocked with the key. This is inconvenient, but I am able to operate the car.
Finally took the car in to the dealer for a diagnostic ($125) and this found that the steering lock assembly is cracked. Replacement is $800, plus I will have to buy a second key fob at $349 (I only have one) to reprogram the new assembly.
They tell me this will eventually break/stop working and the car will not start at all, resulting in a tow to the shop to complete this work.
This is much more than I want to out into a 2009 with 150k miles, but do I have any other options?
any advice is appreciated.

Thanks, I suggested a used part at the dealer, but of
course he said it would not work. I will follow up as suggested. I should be able to at least get the key from another source.