Door Latch failure is an ongoing problem. There are pages of member replies documenting the frustration associated with the Door Latch frailities.
The problem with finding a replacement is complicated by the manufacturer's poor nomenclature. Changes were made to the standard product, as the problem evolved. Undocumented factory design changes made some repair kits incompatible during the interim.
I contacted Customer Support at TriMark. With persistence, I was able to convey my frustration with how complicated something as blatantly simple as finding a replacement door handle is made by their inconsistencies.
After a prolonged wait for a response to my need for a lock capable of spanning the increased door thickness of a Phoenix Cruiser, I was told the replacement kit is part number 40411-01-K. $336.58 plus shipping. I was also told the kit contains the interior handle, exterior handle, 4 keys, strike plate and screws. Curiously, that is what arrived. No retail box. No instructions. No sealed parts bags. No manufacturer's warranty.
In earlier exchanges, the Customer Support's response had always maintained an unwillingness to deal directly with the customer. At that price, it appears they were willing to make an exception. I don't know what the explanation is. Other than bizarre.
Lots of replica door locks on the market. Some available for $125 Trouble is: the less expensive versions contain pot metal parts and are probably short lived for the same reason the original TriMarks failed frequently.
As for using the Deadbolt to secure the door in the absence of a functioning door latch, I was forced to when traveling during the struggle to obtain a reputable replacement. Opens the door from the inside using the locking lever. Opens and locks from the outside using the key. Traveled two thousand miles with no consequences. The door handle was disconnected by the absence of a door latch and flops when traveling. No big deal!