Hi there,

I own a Sony DVD player, DVP-S725D.  (a standalone box) I live in
region 4, and my player is coded to region 4.  But I have some region
1 discs I want to play.

There are several codes I have found out, listed specifically for my
model, which allow the region code to be changed at will.  However
they require the entry of number codes on the remote control.  My
remote control (the factory standard one) has no numbers on it.  So
what kind of remote do I need to actually use these types of codes and
where can I buy one?

http://www.techtronics.com/uk/images/sony/sony-725-X.jpg This picture
seems to indicate that there are indeed numbers on your DVD player's
factory standard remote.
Especially, it seems that you'd have a hard time directly addressing a
scene number if you didn't have numbers on your remote.

Do you have a model number for your remote? 

Also, this review http://www.dvdtimes.co.uk/reviews/hardware/sony7252.html
didn't have any problems with the region swapping between DVDs. But I
understand that you're having the problem, so...

Hi there, yes this is exactly what my DVD player looks like.  But not
the remote.  The remote looks totally different, is much smaller and
definitely doesn't have any numbers on it.  Does anyone know what the
model of that remote in the picture is, as i'm guessing if I can find
one of those it might just do the trick. Thanks for your comment.

You might try a generic all-in-one type remote with dvd support from
your local Walmart or RadioShack-type store (OK, I don't know what the
equivalent storetype is for -- what's region 4? Australia?)