Lets clear this up.
You do not need the flame particle texture to view the flame in-game.
The flame particle just edits the flame emission's look to make it look better.
What you need is an original flame which can be made by using a flame forger.
The flame forger can be opened it game by CTRL+L.
Yes, the usage of the flame forger is free, yet you need the specific amount of Toricredits to make a customized flame you would like.
So its either you forging it with your own TC, or making a deal with someone else who forges and haggling a deal with other payment options aside from TC.