I haven't tried it but have read that Flavor Revolution grape candy is good, not a jolly rancher but if mixed with a jr base might work. FW and Purilum white grape are good to build a candy with. I haven’t tasted the FE sweet grape tester yet but thinking it will be a good candy grape as well.Many moons ago I tried and tried for a Joly Rancher type of grape.
Nothing was out there.