I don't have a part number, but that doesn't make any difference...... Parts like this are almost never available from Colt these days.
Colt only sells parts through Brownell's and Midway USA and they very seldom have any Colt parts at all other then some common small parts like pins or screws.
You might be able to place an order through Brownell's, but don't hold your breath waiting for it.
A more viable option is to buy a quality, name brand safety from Brownell's and have it bead blasted to match the other parts.
It won't be a genuine Colt part but only you'd ever know.
There is one caution on bead blasting stainless and aluminum parts........ Most bead blasters are used for carbon steel parts like car parts.
If you bead blast a stainless or aluminum part in a common auto garage or most machine shops the air pressure can embed tiny particles of carbon steel into the stainless or aluminum and those particles can rust later, ruining the surface.
If you bead blast, you need to either have the blaster cleaned out and filled with new blast media, or use a blaster that's used for only stainless or aluminum parts.
Don't take someone's word for this.
Another factor is the appearance. You get different looks of bead blasted parts depending on the type of blasting media and on the air pressure.