Seat foam is available from VMX unlimited. Fits well and is hard enough to rafce on
I got my cover from I think VMR on ebay, again fits well and looks the part
Seat bases are becoming rare. I understand someone in NSW or Vic is making fibreglass ones but I don't know who
Do you have forks at all, or triple clamps?
TS125/185 and 100 after 74 use the same lower fork legs. inner tubes are different internally as the TS had adjustable preload but externally they look the same. Not sure about length tho
TM triples are alloy where TS are steel
Springs are different between TS and TM. I found TS springs to be way to stiff