A local glass shop should be able to get the IG unit and install it into your existing door panel with no issues. Loewen is a quality product, sounds like a local dealer issue to me. He may be short handed with the pandemic and not have people or the time for service / repair work but that is still no excuse to not at least pick up the phone.

So. The glass shop we contacted, who does a lot of commercial work, says they think our best option us to replace the entire door. Apparently, the grills (2 over 2) complicate things and they don't think we would be happy with the looks if just the glass is replaced. They were going to give us an estimate to do the glass only or replace the entire door, but we never heard back. Followed up, no response. And still no response from the local Loewen dealer.
I really don't want to replace the entire door. Its a three panel unit installed side by side with 3 other units. A new unit will stick out like a sore thumb.
Not sure where to go from here. Grrr.

What kind of grilles? Simulated divided lites? Where approx are you located maybe I can point you in a direction?

Call Loewen direct. Here is their number: 1-800-563-9360 and tell them your story complete with the lack of response from your local dealer. I would also have the size of the door/color etc. in case they need it. Not sure if Loewen uses an etched label on the glass like others but look in the corners of the non broken side and get the number if it has one. That would also help.

Normally, glass only is not a good option with divided lites. They will probably replace the entire door panel. You will be able to reuse the hardware and hinges (if it is a hinged door). You will be responsible to repaint/stain the door unless you originally had the factory do that.

Good luck and let us know how it goes.