i have the best repair for a leaking primer bulb for your average cheap lawnmower, the hole can be repaired by taking silicone of the type used to repair a windshield leak, it is a tube of almost liquid silicone rubber and you paint it on to your primerball covering the red rubbery material all the way and dry it. the bulb will be good as new and you won't have to hunt around for a place that has the exact one for your mower. i have not tried silicone clear caulk but i guess it works too.