These are on eBay all the time- Myself, I much prefer the round case over this style. Here's a link to just one of a few that work on these. If you find one that looks like it's in great condition, but isn't working, then I'd consider having it serviced. On the one you posted, I'd pass.
The Guy >>>
Case refinish - polish & remove all but the very deepest of scratches..............................$75
Case back refinish - includes “factory” circular graining on crown and battery hatch........$75
Astronaut bezel ring refinish (includes cleaning and lubing of bezel ring components).......$75
Clean, Lube & Adjustment movement to run properly of the 387S battery........................$145
Clean, Lube & Adjust "hack" movement for Spaceviews & Railroads.................................$160
Clean, Lube & Adjust "hack" movement for Accutron Astronauts........................................$175
Clean, Lube & Adjust clock movement for Accutron 214 Clocks...........................................$200
Accutron “style” bracelet refinish - polish, clean & remove most scratches........................$75
(Other bracelet restoration services available and quoted on an individual basis)
Complete dial restoration on all 214 model Accutrons including Astros......................... quoted
Complete repair / restoration of genuine Accutron bracelets including buckle..................$125
Replace crystal with “factory correct” or genuine new old stock crystal on
Accutron Spaceviews and Astronaut models..............................................................quoted
Restore original Accutron Spaceview crystal - includes removal of deep scratches...........$50
Restore Spaceview & Astronaut hands - includes replacing luminous...............................$50
Restore luminous on Chapter Ring Spaceviews and other dialed models..........................$75
Restore luminous on Astronaut dials............................................................................$100