There is no such thing as a "Penny Turtle". The name was coined (heh) decades ago by people who raided wild turtle nests, collected the baby turtles and sold them in pet stores and markets (probably in USA, but the same thing happened here in Australia, among other countries). The name "Penny Turtle" was used to help convince people that the turtles would never grow larger than a penny, which in 99.9% of cases was actually true, because of course, most died before growing noticably!
The turtle best suited to you depends somewhat on your location. Likely the Eastern Long-necked Turtle Chelodina longicolis is your best option.