I'd go for a 6BG6 any day. These were one of RCA's first dedicated line scan valves, Brimar got the dies and made them too, so they are in the UK. AWV in Australia made them too. I see there is one on UK ebay now, they have a larger cathode surface area than an 807:
https://www.ebay.co.uk/itm/VINTAGE-B...gAAOSwEfVcTa~b