R7-T1 was never seen on screen, but was briefly Luke Skywalker’s astromech when he flew an E-Wing fighter during the Black Fleet Crisis.  The droid was mentioned by name in the book Before the Storm.  While it first appeared in visual form with Hasbro’s BAD, the look was made official in other Lucasfilm reference sources.  Of course, all of this was rendered obsolete and relegated to Legends status. 

The R7-series of astromechs was manufactured 10 years after the Battle of Yavin, which currently makes them all non-canon.  As an exception, there was a droid in The Clone Wars designated as R7-A7.  The Story Group confirmed that this was an advanced prototype astromech, but was not specifically meant to be an R7-series droid (which came out many decades later).  It was simply named “R7”, but was actually an advanced R2-unit.  (Most of this may not be canon any longer.)  Proper R7 units are indicated by their triangular “eye”.

What you need to build R7-T1:

BD15 Quarren Soldier

BD14 Mon Calamari Warrior

BD12 Padmé Amidala

BD11 Saesee Tiin