3SK131

NXP semiconductor BF998R
www.mouser.com (40 cents)
(Note: BF998 can also be used, if installed upside down.)

2SK520

NXP semiconductor BF545C
www.mouser.com (59 cents)

2SK125

Fairchild Semiconductor J310_D26Z
www.mouser.com ($1.05)

US1090 (diode)

NTE 519
www.mouser.com (48 cents)

RLS73/1SS133 (diode)

ROHM Semiconductor 1SS133T-77 (through hole)
www.mouser.com ($2.40)

2sc3133

Mitshubishi Electric RD16HHF1 (MOSFET)