Heat senor leak on Fuel filter.
 

How to fix small leak on fuel canister ? Its the heater on the top and leaks around the rubber seal,

My drain valve was leaking once, I took it apart and installed new o-rings and it has been fine ever since. First thing you need to do is figure out what/where the leak is, then we can decide the best action to repair it.

its the rubber seal around the heater wires on the top of the fuel fiter mount.

Around the base of the heater, or coming out through the center of the heater where the wires are. If its the latter, new heater would probably be the best fix. If its around the base, a new o-ring.

Its around the outside of the heater. How would you take it out and find the part? Dodge does not sell it and wants replace the whole filter canister

The fix is to get yourself a GOOD lift pump with filters and take the OEM filter housing out. Airdog or FASS.