Trying to locate a power pack, or battery charger for my Aiwa HS-J550D.  Does anyone have any idea where I can, or where I might something comparable?

Welcome Anne, seems your J550 I am not familiar with at all. Be great if you posted a photo or two of it.  You might try www.partstore.com      for the part.  Good luck

The HS-J550D, I think is a variation of the HS-J55, which is similar to the HS-J505.

That being the case, then you need an AIWA 2V 350mA AC-207x

where x can be :

K for UK (240VAC)

E for Europe (220VAC)

H for WW (110/220VAC)

U for 110VAC