Thought I'd add the PCE adaptor I made to the gallery. Looks like it's similar to the idea Chop5 had in the first picture of his first post.
I made it out of an original 32bit PCI extension cable (not PCI-E), something like this:
I removed all but one ribbon cable, cut the bottom PCB to the size of a hucard, removed the pins from one side of the PCI slot and widened the slot a bit with a dremel so a hucard could fit in. Then I cut the traces on the top PCB for the 8 data lines to rewire. The bottom PCB needed a little plastic or tape since it was too thin to make contact in the cartridge slot without it. It's been working great for my use in a Duo. I don't have a TurboExpress to try it with, but it holds the hucard and plugs into the system snug enough that neither would fall out, although the ribbon cable may be a bit long.
Hope this helps anyone looking to make an adaptor. I think it cost me about $6~7.