Vostro 7500 charger part number?

I'm looking for an additional charger for my Vostro 7500. The OEM is 130W and uses a 4.5mm connector.  Does anyone know part numbers and sources?  The charger sold on the Dell site which may be compatible (I've emailed sales) is a whopping $90.00. 

I see lots of chargers on Amazon, and some sport the 4.5mmx3mm connector, but I'd prefer to get the exact same charger that was shipped with my laptop.

Thanks,

Dennis