Wish doesn't have any anime version, so I'm quite surprised that a drama album, a Soundtrack *and* a CD Single have been released O_o
The largest part of the songs have been composed by the "Ali Project" who also wrote a lot of tracks for other CLAMP creations.
I personally really enjoy the music, and if you'd like to sample some of it, you can head on over to the download's music section. ^^

Audio Sphere : Wish Music CDs

There have been very few realeases of Wish-related CDs, and unless an anime is produced (haha -_- ) , I assume there won't be any more.
In this little section you will find the basic info for the releases and where to purchase them online ^^

the wish soundtrack
The Wish Original Soundtrack
Produced by : Viktor Entertainment
ID : VICL-2181
Tracks by : The Ali Project
Released : 1997
Availability : in Distribution
the wish drama album
The Wish Drama Album
Produced by : Viktor Entertainment
ID : VICL-5337
Released : 1997
Availability : ?

Anniversary of Angel Single
Wish Gift Box : Anniversary of Angel
Produced by : Viktor Entertainment
ID : ?
Released : 1997
Availability : Seldom; check eBay
note: This single is only available with the Wish Gift Box set. It is not sold seperately!

Where to purchase them

I'll admit that I'm not exactly an expert in finding anime merchandise online (partially because a lot of the shops don't ship to where I live, so I have a hard time finding ones that can provide me with CDs ), so if you have any further info than what you find here, *please* tell me. It would be so greatly appreciated !
I can't seem to find the Wish Drama Album anywhere online, so I can only give some info for the OST.

Wish Original Soundtrack
Purchase at Animenation - http://animenation.com
Price : 24.95 US $
Purchase at VOE.com - http://www.voe.com
Price : 14.95 US $

Seeing that Animenation carries it, I assume it's still fairly "easy" to get a hold of.
They do accept international orders, so I was pretty much in 7th heaven when I noticed ^^
Here are their charges for international shipping:

Postal Air Mail - $11.95
Postal Express Mail - $25.95
UPS Express - $29.95

Since it's only a CD, you won't have to pay any extra charges (like with wallscrolls or other large items)