Aiks, I only research on N46 engine, now pulak need to research for N52.. darn... I should have bought N52 in the first place..
Wait, I'll get u the part numbers.
Update:
N52 is debuted in 2005 and first car to adopt this engine back then was E60 523i, year 2005. I have check the catalog, this model has 2 oil pan design, one of them same like yours but both also no dipstick. So confirm no OEM parts for u unless you want to use the E46 M54 dipstick to modify (O-ring size also different at the oil pan mount for the M54 dipstick guide tube).
Check out the side of your N52 oil pan, there is a hose (thumb size
) going in now, that's you oil return hose and that's where u gonna stick in your dipstick.
More about N52 here, with loads of photo for your engine..
http://www.mwerks.com/artman/publish/features/article_960.shtml
On the other hand, E90 N46 can use the following E46 N46 parts to install dipstick..
1) 11 43 7 505 490, Dipstick
2) 11 43 1 717 666, O-ring
3) 11 43 7 505 011, Guide tube
4) 07 11 9 900 268, Hex Bolt with washer
5) 11 43 7 509 343, O-ring (Production discontinued)
6) 12 52 1 732 530 or 11 78 7 549 563, Cable clamp