Hi!
Q1 is an industry–standard dual MOSFET, each transistor is rated 50 V 3 A, Rds 130 mΩ, Qgs 2.2 nC, Ciss 250 pF, ton 5.1 ns, toff 15 ns !
The two individual FETs are wired in parallel.
Pinout :– Pin 1 Source 1, Pin 2 Gate 1, Pin 3 Source 2, Pin 4 Gate 2, Pins 5 & 6 Drain 1, Pins 7 & 8 Drain 2.
Full type no. is IRF7103PBF but any dual MOSFET that meets the above specs and pinout will do !
Chris Williams