Hi,
There isn't a way to do this out of the box, but you can do it programatically -
tk2dTextMesh tm;
Vector3 pos = tm.GetComponent<Renderer>().bounds.center - new Vector3(tm.GetComponent<Renderer>().bounds.extents.x, 0, 0);
That gives you the middle left position, you can position the sprite at that position after changing your text.
Alternatively, there may be an easier way to do this. If you add your sprite as a glyph in whatever package you create your font with... you can map it to a character you don't use. For arguments sake if you've bound it to $, you could just type out $ 3000 and it will always be aligned correctly without any code.