This is an old post, preserved for reference.
The products and services mentioned within are no longer available.
This post has been left for historic information. The PET microSD is no longer in production. The replacement SD2PET is available now, more information on the pre-order page.
The latest batch of PET microSD boards are ready, and they have changed a bit, they've gone blue!
There are also a few other minor mods, most notably the package of the 74LVC125A buffer has been changed to give more room around the other components. The power LED is also now blue to match, with green for activity, red for error.
petSD+, available from Dave Stevenson. Here it is without the display:
2022 Update: I have since designed a much nicer SD drive for a PET. The SD2PET is available from The Future Was 8 bit