There may be some specialised (probably very expensive, and hard to find) flash units designed specifically for such usage, but off the bat, I would say something like the metz 60 series flash might fit the bill nicely, are still available (more likely on ebay) and are renowned for their reliability and robustness, besides accuracy both in terms of exposure and color temperatures. Some units in good condition and more than 20 years old perform more predictably than many modern flash units as long as they've not been thrown off the side of a building and the batts have been maintained properly.
Google Metz 60 ct4 to find out more, and Try to PM Larry the Mod; he might still have one in good cond for sale.
CHEERS!