Very good question, i was just thinking the same. If I can't get hold of one i was thinking of taking the front section of lid off and putting a sheet of hardboard over the gap then i could cut a hole in it for the feeder. It won't look very pretty but i'll be on holiday so who cares. Of course you could go over the top with this, make an exact copy of the plastic lid to fit and paint it black. I have to have someone stay at my house anyway to feed the guinea pigs, rabbit, hamster, frogs etc anyway so i might just put the food in individual bags and let them feed the fish.
Emma