If you don't mind descending into a rabbit hole ;-) there's also the LEC series of Spectrum rebuilds, developed over at the tliendhard forum. The hardware is close to the original, and amongst other things includes LEC memory expansion, so you can run CP/M, and the Interface 1 is integrated into the board. https://forum.tlienhard.com/phpBB3/viewtopic.php?t=4598