Can you fit a Kettler Flipper on an Electra Townie?

I'm looking into buying an Electra Townie or Cruiser and I want to make sure that a Kettler Flipper or Teddy will be able to attach onto it. It has to be one of those two seats because the weight limit goes to 50 pounds on them and my son is already over 40 pounds (which is the standard weight limit on other child seats). The guy at the local store didn't think that a child seat would attach to an Electra but I was wondering if anyone else knew differently. Thanks for you help!