I believe that you can by derrailleur hangers that fit slotted dropouts so that part is possible. But if it's a dedicated SS then the dropout spacing will be too narrow to allow fitting a geared wheel by enough that it will be a serious factor.

Finally there's LOTS of great riding bikes out there that will feel just as good as this one. And given all the things you have going against you on this conversion I'd just keep this one and enjoy it for what it is or sell it to finance a geared ride.