Attached is a model that approximated the GW 3303 - channel 3 with 2 modifications to reduce the peak on turn on and CC-CV transition.
The added parts are R12 and C5 (the first step of modification) and
C8+R13+R11. The second change only make sense together with the first change.
I chose the LT1057 for the TL072 and the IRFP250 instead of IRFP150 to use only parts from the std. lib. R1 is changes to 0.15 Ohms to include resistance of the wire. The current part is missing the extra amplification step and thus might react a little different.
I notices that an easy change would be reducing the positive supply voltage (initially I had a lower value and thus smaller peaks).