For uv lights, check out sites such as Amazon (as well as eBay). Search for "uv light torch" - various makes, at various prices are available, but best to avoid the very cheapest as they may be too small and not have enough strength to be of much use.
Probably best for now to ignore the "shortwave (around 254 nm [nanometres]) uv" versions as extra care needs to be taken that shortwave uv does not get into the eyes or on the skin. Longwave uv (around 365 nm) light is generally safe to use without protection but always best not to stare directly into any uv light.
Basically, for "Vasart" items when longwave uv is directed at the clear glass it will show a definite bright or dull green reaction. If there is no obvious colour reaction, (other than the sometimes seen "purple" which is usually a reflection of the uv bulb) then it is unlikely to be a Vasart piece.