GunBroker "sold" prices are market prices. A price above or below those prices would be "crazy." You will have to be "crazy lucky" to find an example for substantially less.
In my personal opinion, a Colt Model O Commander is needlessly big and heavy, and of limited magazine capacity, for the little 9x19 cartridge. If one is going to go down to the 9x19 cartridge, then an appropriately small and light pistol with greater magazine capacity would seem the more logical choice. My personal choice for a 9x19 carry pistol is a Kel-Tec P11, which is about the size (but thinner) and weight loaded of a Colt Cobra, and has a cartridge capacity of 10+1.
If you still want a Commander, then get ready to pay market price now, or hope for a "crazy" (low-priced) example to appear - sometime.
If one is planning on customizing, then perhaps it may help to expand the search to include the Colt Commander in 38 super (which may be even better), and getting either a Colt factory 9mm barrel or an aftermarket one. Often the swap is relatively simple - in many cases, just the barrel and a 9mm mag.Wanting to find a Colt 9mm Commander and have it customized to carry.