It seems that you've gotten no answers, sorry for that.
Side play in ANY trigger can be easily eliminated by shimming.
If you feel confident about your mechanical abilities, get some cheap spark plug set of feeler gauges. Dismount rear block (do not disassemble trigger).
Using feeler gauges determine what is the amount of "play" that needs to be removed.
Use TWO shims from the same feeler gauge set (that is why it has to be a cheap one) that ADD to the play you want to remove, one shim on each side.
You can punch holes in thin steel using handtools and that will allow to make a calibrated set of washers.
Yes there are metal triggers that will substitute the plastic T-05 ones, and there is a new trigger assembly coming, it's an adjustable trigger that will be labelled the TO-6
I am glad your 460 is earning it's keep. Most Dianas do.
Un Abrazo!
H�ctor