Not sure if this is new news or not, but first I've seen...
Also never had any experience with Mugen, but generally hear good things about them.
Mugen's site says they're out of stock, but it looks like they're available on Ebay. Caveat emptor on the legitimacy of those... though they're reputable sellers, and the picture in the second one is identical to the one on Mugen's site.
I'd love to avoid the extended on this phone that does me pretty good already... so every little bit (that can fit in the stock case) helps!