Alexcarp,
Many of the smaller parts used for the B250e are the same as that for the B-Class ICE car and for the C-Class cars. You have to check the MB part number to be sure.
I have had good experience in buying new or used car parts off eBay. Try to look for parts company like eurocar. I bought some taillights for my ICE 2006 E500 wagon and they would not ship me the part without verifying the part fit my car using the VIN number. In this case the parts were brand new OEM (last one).
With the line being discontinued, getting parts from the dealer will be tough unless it happens to be the same part number as an active model like the B-Class ICE car or the C-Class. Dubious that they stock many B250e parts anymore. However, they can help you identify the right part number unless you can pull it off your damaged part or off a B250e parts manual.
You should be able to get it replaced. Good luck.