RB Micro (Colorado) specializes in Astatic D-104 parts and restoration.http://www.rbmicro.com/index.php
Sources for Straight Microphone Cordage can be found at almost any Guitar Center or audiophile/musician shop. This cordage is primarily 2-conductor with shield fir Balanced Microphones (using 3-pin XLR connectors).
For RADIO usage (Audio and PTT), Belden (old 8496, 3-conductor) and Alpha sell coiled cords used for LMR and Public Address systems. Major US distributors stock more popular versions.
Heil Sound sells their Heil Cable with 2-conductor for PTT and shielded audio for microphone.
You can find Taiwanese imported cables on eBay and most CB-shops.