The only places Ive been able to find such connectors is at Mouser, Digikey or Ebay. With a smaller connector I think Mouser or Digikey are your best bet.
Youd have to do some research into the AMP connector catalog to pull the part number, then you can search the sites for it.
I dont know what the connection on the 4500 looks like compared to the 2500, but I know there is a thread around here somewhere that actually specifies the parts needed for the 2500 connector (looks like you already have that on one end of the cable).
Would the 6 pin connector fit onto the 4500, spacing wise? if so, it could just be a matter of moving the conductors to line up in the 6 pin connector to match what the 4 pin connection is expecting.
EDIT: I know its not the greatest solution, but you can probably get away with pulling the pins out of the existing 6 pin connector and then just sliding them right onto the corresponding pins on the 4500. If you are worried they might fall off, a little hot melt glue around the connection would help with that.
Youd have to do some research into the AMP connector catalog to pull the part number, then you can search the sites for it.
I dont know what the connection on the 4500 looks like compared to the 2500, but I know there is a thread around here somewhere that actually specifies the parts needed for the 2500 connector (looks like you already have that on one end of the cable).
Would the 6 pin connector fit onto the 4500, spacing wise? if so, it could just be a matter of moving the conductors to line up in the 6 pin connector to match what the 4 pin connection is expecting.
EDIT: I know its not the greatest solution, but you can probably get away with pulling the pins out of the existing 6 pin connector and then just sliding them right onto the corresponding pins on the 4500. If you are worried they might fall off, a little hot melt glue around the connection would help with that.