Many of the auto parts stores carry the jump packs. I have one but do not remember the brand name. I do recommend the unit with the "strength of charge" lights that are green, yellow and red, so you always know the strength of the jump pack. Forty dollars sounds about right, buy I would check with a few auto parts stores or tractor supply stores in you area before purchasing. Also, check out Max Tools website. They carry this unit and many others that are useful for Stovebolters.