Determine the cross section of the old gaskets and go to someone like Grainger or McMaster Carr and buy new stock. Look for weather stripping. Buy some glue to keep the new material in and to glue the ends together
an wise old sage on here one recommended using shaft packing as it lasts forever if you have ports that it will fit....bunched cheaper than some factory replacement gaskets and if the same size as your shaft packing and endless supply of spare parts...I might try it too.
oh I'm sorry you posted in the title Cha Ching $$$$ trawler...go for the good stuff...sorry couldn't resist...