You should be able to just buy new bulbs, you don't need new ballasts

 

Just try to find the spacer and buy it?

HID MAZDA Xenon Bulb H7 Holder Adapters Spacers Mazda 3 | eBay

I know it might not be the one you need exactly but try picking that up before you go buy new headlights

 

The trimming is only to allow the square spacer to fit into the round hole of the bulb socket in the headlight housing. Im not positive, but trimming to much shouldn't hurt anything. I didn't even think of this when doing mine and just started snipping away..

From what I remember the spacer just slides over the back of the bulb maybe it's jammed to far on the bulb?, any way to try backing it off the bulb 1-2mm? You're saying that the wire clip won't hold the spacer snug anymore right? Any way of slightly bending the wire clip to give more holding pressure on the bulb? just throwing some ideas out there.

 

it sounds like youre leaving those black plastic spacers out. When I put mine in I forgot the spacers at first and had the same outcome they just sat loose..

 

+1, I had the same problemo.