Your best option would be to find a used Play:5 (Gen 1) on sale on eBay or Mercari “for parts only” or just purchase a used Play:5 that is still in good working order. You can get one used for $140-$175.

I’ve never heard, in all my years of being on these boards, of Sonos supplying replacement parts. Whole item replacements where the device was in warranty, but never parts for repair.

Sonos is a “end of life” (EOL) product manufacturer. When the product is no longer operable and/or out of warranty Sonos will make concessions in some instances to replace the product with a current model at a discount. 
 

There is also the Trade-up program for a like product at usually a 30% discount. The nice part about the program is there is no stipulation that the product be in working order. In fact if the product is operable you can get the trade up discount and sell your old product. The new owner will not be able to use the product for the trade-up program.

What one has to understand is that Sonos speakers unlike analog speakers will reach a point wherein they cannot move forward with upgrades due to software and firmware limitations. While they may still work… at some point they will be unusable. The Play5 Gen1 is a good example of that happening. Electronics wear out. Analog speakers typically fail because of the material around the drivers becoming brittle. However analog speakers will typically outlast Sonos.

If you’re not prepared to accept that Sonos may not last as long as analog speaker then consumers should not invest in them. I understand that reality but at my age my Sonos will most likely be useable after my life-warranty expires for my time on earth.