If Seiko have no Windows 8 driver for it on their support website, that's pretty much end of story.
Don't be too hard on Seiko though, all the PC hardware manufacturer's have to draw the line somewhere when a new version of Windows is launched. Same applies to all computer peripherals which need a third-party driver.
They all draw a line at supporting older models (some not as old as yours) because having new drivers written isn't cheap and it's a very competitive market. If they had to have new drivers written for every model, old as well as new ones, they would sell fewer new products and that's bad for business if you can look at it from their point of view.