I recently purchased my entire system (M1 Gold, 8 Keypads, 2 Power Supplies, 6 Input Expanders, 3 Relay Cards, etc) through Orchestrated Home. The reason I chose them was because they were very responsive to my initial email and they have everything listed (either in stock or available) on their web site. Some of the other online places I checked out, either didn't return emails, didn't have everything listed, or prices were much higher. I reached out to them with a list of parts I needed and they quoted me their best price on the order, which was less if I had ordered everything directly from the web site. So I would suggest you email them directly and see what they say.
I did have two issues, and they promptly resolved them. One of the adapter plates I ordered, a couple of the black plastic rivets were broken in transit - they contacted Elk directly and had them send me replacement rivets. And a keypad I ordered was faulty - I'm still in the process of resolving that with them (just need to send them back the bad one) but that should be finalized this week. So their customer service is excellent!
Good luck!