Solders onto the old solder-coated connectors on your Model I and Expansion Interface, and replaces them with gold coated edge connectors like it should have been in the first place:

You get:

4x 40-way Goldplug-21's: M1 KB, EI bus, EI RS232, EI HDD (aka screen printer port)

2x 34-way Goldplug-21's: EI FDD, EI LPT

Postage is $12.50 worldwide.

NOTE: soldering is required... it's not difficult but does require disassembly of your Model I and EI.  Clean your edge connectors one last time with a pink pearl eraser before soldering these on.  If you lack soldering skills, get someone else to put them on.

NOTE 2: needless to say you can't put the plastic cover back on the EI or keyboard, but it's a small price to pay for the increase in system reliability.