Replacement Dell 9020 SFF system board

Hi.

I need a replacement system board for a Dell Optiplex 9020 SFF (small form factor) desktop.

Could anybody give me advice on where to get one, and/or whether any other models are compatible (is the 3020?)?

It seems that Dell do subtle changes across different models, eg. the placement of the I/O sockets, and so-on, which makes the board apparently specific to that particular model.

It would also be interesting to know whether there are any 3rd party boards which will fit the 9020 SFF? (I suppose that's unlikely though...)

Thanks for looking.