I own several Fujica ST-series SLRs and they are a delight to use. They have brighter viewfinders than the Spotmatics. They are somewhat rare, however, in N. America and are now commanding $50-100 on eBay.
Another alternative would be the Yashica TL-Electro. I own one and the viewfinders are similarly bright. The TL-Electro also has mirror lock-up and a higher flash sync speed (nominally 1/125 sec, though likely 1/90 sec in actuality) than most M42s.
Best of all they can usually be had (with the sadly flare-prone Yashinon DX 50mm f/1.4) for about $30.