Upload & Sell: On
The current Canon flashes are all TTL exposure based and don't have the auto-thyristor 'eye' on the flash to vary light output based on camera to subject distance. Therefore, the current Canon flashes will only be usable on manual power output, and not all models have manual output settings. The Canon flashes from the AE1 era were all designated with an "A" suffix, such as 155A, 199A, etc... and there are probably some still out there on the used market. Sunpak also had some with interchangeable hot shoes that would work similarly, with the correct Canon dedicated shoe.
Otherwise, as everyone suggests, the Vivitar 283/285 would be a good solution. The only benefit to a flash with Canon dedication is it would set the camera at 1/60 and might even set the aperture based on the aperture/power output selected on the flash (with the aperture on the lens set to A).