Live Steam Models offer a range of firing irons that suit the engine. I bought my firing irons from there. For the 3" Burrell I would recommend that you make your own set. You should make one shovel, one round poker and one ash pan rake. These are quite easy to make. Just make your own dimensions to suit your engine and your style of firing.
If you sit quite far back when driving the engine, I would advise that you make the handles for the irons plenty long enough. They may look a tad out of scale but it's a practical solution. I would also advise that you make your shovel long. The fire hole isn't very wide so you want to be able to get more coal on the shovel length-ways.
Dan.