I double checked the number on the parts list and it's right. When I examine the mosfet itself, it says 252 with the motorola insignia and 182023 stamped below it. Hope this helps.When I Googled it , I came up with a site, I think it was American Semiconductor, that says they have for $15 and change plus shipping, but again, no complete datasheet, just basic specs.
Thanks,
Bruce
Here's the specs from that site
MPF122
Motorola, Inc. :: N-Channel, Dual-Gate Tetrode MOSFET
Specsheet / Datasheet
V(BR)DSS (V)=25
I(D) Abs. Drain Current (A)=30m
Absolute Max. Power Diss. (W)=500m
I(DSS) Min. (A)=20m
I(GSS) Max. (A)=20n
g(fs) Min. (S) Trans. conduct.=8.0m
g(fs) Max, (S) Trans. conduct,=18m
@V(DS) (V) (Test Condition)=15
C(iss) Max. (F)=7.0p
Status=Discontinued
Package=DIP