The code you're getting is for a small evap leak. It's partner in crime is the 0455 gross evap leak. Both can be a nightmare to track down. The evap leaks are fairly common over on the XJ side - but those are older models with typically more worn out parts/lines.
Best thing I could recommend is to give all the evap components and lines and connections a good lookover. A small leak could indicate a minor crack or pinhole in a line or connection. There should also be a green cap (access port used for smoke testing usually tagged with a 1psi max) at the purge solenoid. Check that the cap is tightened all the way.
Many cases getting a smoke test is your best bet from what I read. I've been trying to track down a gross leak 0455 on my XJ for over a year now to no avail. However, other than possible issues getting the rig to pass emissions regs, the emissions evap leaks really shouldn't effect how the rig runs. For this reason, I haven't dedicated a lot of time trying to fix it. It also hasn't prohibited getting my tags for the Jeep.
Other thing I can think of is to disco the battery for 10 minutes or so to reset the code and see if it comes back. You mentioned replacing the Leak detection pump and gas cap but sometimes if the code isn't reset it will still pop the check engine light.
My Build Thread WK
My Other Build Thread XJ
'01 XJ with some stuff
Sept 2013 Cherokee of the Month
'07 WK with some other stuff
~RED WK CLUB #7~
'11 KK with mostly stock stuff
'06WK our first Jeep with stock stuff - totalled and gone