Ye Olde Tyme mechanical timers from Canadian Tire should work. The only challenge is finding a 3-prong one for a grounded circuit.
https://www.canadiantire.ca/en/pdp/noma-indoor-grounded-timer-24-setting-0528823p.html#srp
Unlike the electronic ones that can program 48 day-night cycles, account for daylight savings, and other things that are overkill for this application, the olde tyme mechanical ones can have all the pins pulled out so it’s always on. Check the estimated print time on Cura (it’s usually pretty accurate) and add an extra 30 minutes to an hour then press the appropriate pins in from that time forward.
Having said that, the power drawn by the fan and motherboard are fairly low and don’t realistically pose a fire hazzard (at least no more than your microwave of fridge do), so I just leave mine on.
I did once find a pair of Intermatic Model TB121 24hr digital timers that I use on the battery chargers for my tools. It’s basically a remote (wired) on/off switch that can be programmed to turn itself off after X amount of time. That way I charge my batteries for an our and don’t have to worry about shutting it off since it could be weeks before I need them again. You could do the same thing with a printer. Unlike Ye Olde Tyme mechanical solution, you can’t really program it on the fly. That is to say, you’d have to program it, then shut down the printer and press “ON” to have it run for the desired amount of time, then start the printer whereas the mechanical beasties can be left running all day if you want and set to turn off on a whim, even if you’ve already started a print.