I assume that you're referring to a float that's specific to your mower as I just checked for my 10247 with float #95-899 and it's available. Could you mod one of these or another that is available to work in your mower?
As a member of the Antique Outboard Motor Club, many have posted that the best product is Model Airplane Fuel Proof Dope, used to protect paint from the Nitro fuels they use. Let the cork dry out and apply a few coats. Available at most hobby shops.