Harry Amass and Shea Lacey would be interesting additions.
What's your knowledge like of United's youth setup? Admittedly mine is very limited! - but from what I understand, both of those lads are considered as especially promising. Those two and the U18s captain Finley McAllister would be strong on paper, but Amass can only play left back (which is a very short term need), Lacey is a left footed right winger (we have two of those!) and McAllister is more of a holding mid.
There's a right back called James Nolan that regularly covers at left back - perhaps that would be more prudent given he could cover for Eddy and then move to the right if he's absolute mustard?
There's a centre half called Louis Jackson who fits the bill, Scotland youth international and has trained with the forst team - but do we have a need in the area? Someone quality to partner Baines?
There's a central midfielder who has been recovering from an ACL injury called Ruben Curley, who can cover for Isaac and Elliott but crucially can do so at No10 too, like Maxi did.
There's a left winger called Ethan Williams who has posted impressive G/A stats and has bounced between the U18s and the U21s - if he's available I can understand if we've been dragging our heels on Alex Newby as we already have five permanent wingers on the books, Alex would be a sixth.
Finally(!) there's another Ethan - Ethan Wheatley - who is a centre forward with impressive goal stats - but so did Joe Hugill and at a higher level (U21s), which didn't translate to goals here.