You might try McMaster-Carr for your girthy plugs.
As Gomer noted above, it might be someone other than ourselves putting our backup plans into use. For example; power goes out while you are a state away and the Mrs. has to figure out how to get the backup power going, and she may have been too busy rolling her eyes during the weekly SHTF drill to know that this breaker over here has to be switched off or on before this one lest the house burn down or a lineman gets fried somewhere. My dad remedied this concern at his house with a handy laminated card posted next to the breaker panel and one next to the generator to go line by line with the breaker/transfer switch directions and the generator start up procedures. He then labeled each applicable breaker, switch, ect with a number corresponding to the instruction lines.