Well its official, you can get a true 2000mAh battery going in your sl-5500 without spending $70 or doing any hacking (other than grabbing a nail file and filing off a small plastic tab on an EA-BL08 clone), and it even looks nice.
Just get that battery cover linked to in an earlier post of mine, and a Cameron-Sino brand EA-BL08 clone
The replacement cover didn't go on as easy as the original. It took a little gentle working to get it all sides of it down and level against the Z, but once it was, it slid to the left, and the power switch slid up locking it all into place.
I will probably try to get the battery discharged to about 10% today, fully recharge it, and then see how long it can play oggs with mplayer with the screen off. I normally got 7 hours on a regular size battery. From what little i've seen about these batteries in this forum, this battery is known to work great in the models EA-BL08 is for, so i'm not worried.