Following his arrival in the summer, Harrop scored four goals in 18 appearances for Stalybridge in all competitions this season.
However, the former Liverpool Academy player's departure from Bower Fold was confirmed earlier this week.
He has amassed a wealth of experience in non-league football, featuring for the likes of Nantwich Town, Ramsbottom United, Altrincham and Curzon Ashton.
Avro currently sit fourth in the NPL West Division - a point behind Stalybridge - following their promotion from Step 5 in 2022/23.
Manager Alex Frost said: "I am delighted that we have been able to bring Max on board.
"He will add a level of technical ability that this club has never seen before, and is a match winner who will also provide valuable experience, having played in the Conference North for Altrincham.
"Attracting someone of Max’s calibre is another indicator of the progress the club has made."