Hilltoppers isn't alone in the market as well – there are no-name kits with the same target market of people who are handy with a spanner; Swytch [1] also offers kits, but their emphasis is on compatibility with the widest amount of bikes possible (i.e. they have a battery design that latches onto to tubes, racks, etc; and I'm told they provide a torque arm by default on kits so that people with used road bikes don't grind up their forks.)