Boat trailer with no title. Im trying to buy a bass boat and trailer from my buddy

Trying to buy a bass boat and trailer from a friend. He has the title for the boat but not the trailer. They both came from NJ. The trailer did have a bill of sale but the paperwork got lost when he moved house to house recently. What can we do to try and get a title for this thing? I know for a fact it isnt stolen. Tha ks for any insight reddit. I know PA is a pain with titles