Maybe you can buy an unpopulated DDS-60 Daughtercard board from Midnight Design Solutions here:
https://midnightdesignsolutions.com/dds60/index.html
The DDS board is described here also:
http://cwtd.org/Jun4.html
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Dave - AC2GL
All typing errors are my own work and subject to copyright laws,
except errors by the spell checker which are open source.