How can I get "primed TNT" in my inventory?

Is there a way I can make it so when I place an item it places primed TNT (flashing TNT that is about to explode)?

You're going to have to use some command tricks to do it, but it's actually pretty simple to pull off.

First, pick a spawn egg. Any spawn egg will work but I wouldn't choose: Withers, Ender Dragons, Spiders, or cave spiders. (The bosses are obvious, but the reason I wouldn't choose the spiders is because when they are invisible their eyes still glow.) I will choose mooshrooms because the spawn egg's color scheme looks like TNT's.

Next make a repeating, always active, unconditional command block that says:

effect @e[type=mooshroom,name="Primed TNT"] invisibility 99999 0 true

This makes them invisible so it will hide the death animation. Next, in a chain, always active, conditional command block say:

execute @e[type=mooshroom,name="Primed TNT"] ~ ~ ~ summon tnt

This summons TNT. Next, a chain, always active, conditional command block that says:

kill @e[type=mooshroom,name="Primed TNT"]

This kills the mooshroom effectively replacing it with the TNT.

Now rename a spawn egg Primed TNT in an anvil and place it down and you have TNT! You can change the name to anything and you can even include formatting codes ( § ), just make sure you exchange the names in the command blocks for something exactly the same, including the formatting codes.