I've used flash bars many-many years ago; once had an accessory that let me use a flashbar and anywhere from 1 to 5 bulbs at once on a hot shoe (with ISO 400 film, lemme tellya, that could really reach out; feet GN was something like 450 with all five bulbs).
Like any other magnesium flash, flashbars haven't been manufactured in something like 25 years. The thing to do is look for a Polaflash, an electronic unit that replaces the flashbar. However, do be aware that flash photography with the 600 film conversion will be a trial, because the camera sets the lens opening via information from the focus, and you'll want it two stops smaller with 600 film. Simple solution: mount a permanent filter on the flash unit, so you cut the output by two stops.
Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.
I have three. The different finishes had nothing to do with the camera and were just marketing; all were plastic & vinyl. The changes were slight, like addition of a tripod socket in later models.
The SX-70 is still the most expensive photo product ever produced, and one of the most advanced. The camera failed to remain a competitive product. It sold for a fairly high price for its day and of course the film has always been expensive. I understand that time zero has now been altered to make manipulations near-impossible.