Can You Get Magmortar Without Trading in Shining Pearl?
Direct Answer
Unfortunately, no, Magmar can only evolve into Magmortar through trade, regardless of which edition you play. According to [insert source], Shining Pearl, and Legendary Pokemon. However, do not lose hope as I shall reveal alternative ways to complete the Sinnoh Pokédex and discuss its evolutions in various generations.
The Path to Magmortar Evolutions
Magmar has to hold a Magmarizer item in its possession to evolve into Magmortar, only during a trade, whether online or locally between gameboys. There isn’t any alternative way in-game, including completing quest chains or participating in Events that offer this item.
You need to get an in-game item, so consider playing with a different generation.