For my lost TriMark keys, I went directly to them!
I have 4 keys to my Bounder, the Freightliner ignition key, which it's been said that you can only get that from Freightliner (please, no discussion on this).
The 3 TriMark keys, one goes to my deadbolt on the entry door, one goes to the 'other' lock on the entry door and
to all of the lockable bins except for the water/sewer compartment door, and the 3rd key goes only to the water/sewer compartment door. I purchased a replacement key to that at my non-CW RV shop.
The RV shop had the blanks for the other 2 keys but could not cut them. I looked up TriMark and found TriMark
Service & Replacement Parts on the web. Called them, spoke with an extremely nice lady, and ordered 3 of each of the precut keys that I needed for $3.00 each (plus a $10 charge for the total being under $100). The keys were mailed to me and I received them in 3-4 business days.