If there wasn't an obit for him in Iowa finding one on him in Pennsylvania is indeed a long shot. Your best shot is to find data on the people around him including his widow and children. BTW it helps a great deal when you include data on them and not just him.
I'm assuming this is the same Henry Peters who was married to Elizabeth and had children James, Noah, Emmanuel, Amanda and Henry and lived in Madison and Union Counties, IA. According to the census sons James and Noah were definitely born in Pennsylvania which means he married Elizabeth before leaving Pennsylvania. Noah's 1895 Nebraska marriage record shows his mother's maiden name as Ansly. According to the California death index Emmanuel's mother's maiden name was Ansley. The 1850 census of Madison County list some Ansley's who were from Pennsylvania. They just might have been related. Find out where in Pennsylvania they came from and you might find Elizabeth was from the same place. Chances are great that Henry was from nearby.
Fortunately Nebraska started recording deaths statewide in 1904. I suggest getting their death certificates as they might have exactly where in Pennsylvania they were born (if you're lucky). The same is true of their obits. For that matter the same is true of many of the records concerning Elizabeth and her children such as marriage records, death records and obits. The chances are good that at least one record on Elizabeth or her children will have where in Pennsylvania they came from and it is not possible to be certain which ones. Naturally knowing where in Pennsylvania they came from will make your quest considerably easier.