Should be able to get a cheap gillet from Primark/TK Maxx. Get a stupid hat from somewhere, a girls floppy hat would be alright. Put loads of safety pins around it, get some wellies or big boots. Make a comically bad fishing rod out of a couple of bad newspaper inners and string. Boom, done! You could also make a net quite easily.
Rub your skin with any cheap to buy over the counter fish, then wear normal clothes. You wouldn't expect a surgeon to come round for a dinner party in blood drenched scrubs, so why should a fisherman be any different?