I got an email ad from MTC that included "new old stock" NS-508 mics they had found stashed away & were selling for $39 (mic only, no cable).  I looked up what I could find & ordered one figuring it might be a possibility for either the TS-590S or the TM-732a VHF/UHF on the bench since I only had the coiled cord hand mic for the 732.  

Turns out it was a good match for the TM-732a.  The pinouts on the RJ-45 connectors match up so I could get away with just using a cat 5 patch cable ( I did wrap a half dozen turns around a type 61 toroid just before the radio connection).  All the buttons on the mic work fine with their labeled functions on the radio - calling freq/ VFO/ MR/ PF/ UP freq(channel)/ DWN freq(channel)/ power/ ptt/ lock.   The TM-732a supplys power so no need for batteries.  Got a "good audio" report when I went up on a repeater 48 miles down the road even though the mic was currently set for SSB rather than FM.  I have not adjusted the volume setting on the mic from the stock setting.

Don't know how it would work for the TS-590S as that would require an RJ-45 -> 8 pin round DIN type cable & I don't have a spare round connector to build from at the moment.

A linked image from universal radio:


ETA - I've made a few more contacts with the TM-732a /NS-508 combo and the reports are uniformly good.  For those who mentioned a preference, the SSB setting had a slight edge over the FM setting - but most just said "they both sound good"...  I like having a desk mic on a base unit, so this looks like a keeper.

Nick