Is the Cirrus Vision SF50 the only civilian monojet currently on production?
Multiple VLJ kitplanes have been on the market for several decades now; probably the most famous of which was the Bede BD-5J which gained fame in the 007 film Octopussy.  BD-5Js flew in airshows with the Coors Light Silver Bullet aerobatic team.
A supersonic VLJ kit called the Bede BD-10 was planned and flyable prototypes were produced.
And multiple companies have come and gone, offering everything from VLJ kits to wishful thoughts such as the ViperJet to MaverickJets to Stratos.
But near as I know the Cirrus SF-50 is the only certified single engine civilian aircraft for sale today.  Eclipse came close with its E-400, but it only remained a technology demonstrator.
The only other single engine jet airplanes on the market are military.  Aero Vodochody's L-29 and L-39 jet trainers are popular with civilians and air race teams as are MiG-15s -17s, -21s and even a few MiG-23s.  Western fighters like the F-86 Sabre, the Folland Gnat, the De Havilland Vampire, and the BAe Hawk are also popular.