I bought a used flash Tintron MD822 for 250NIS (~60$).
This flash should be used with Minolta but I modified it a little and use it with my Nikon F4S.
It's a great flash for a price I paid.
Tintron MD822 has two flash bulbs, on the rotary head and one on the body. It's possible to operate with the two on the same time.
Flash can work on manual mode or auto exposure. There is a switch to set the aperture selected on camera and film ISO sensitivity.
Flash has 4 zoom position that let to use lenses 28-135mm. It's fully charges for about 7 second lets take few pictures continuously.
The guide number on ISO 100 is about 28GN.
This flash can be used with all old SLR's that have hot shoe.