WHERE CAN I ?

Find a turn signal switch for a 73 Chally? I work part-time @ Advance, we can't get one for him, and I told the customer I'd find one or help

Where can he get these sortof parts? ePay?

Order him a STANDARD MOTOR PRODUCTS TW7...
Rock Auto...

Just my $0.02....

I do find NOS stuff on epay quite often. If you're patient you can often find it and at reasonable price, but it can take time. If you have part number and do frequent "Mopar (part number)" searches you might get lucky. I've concluded, as many have, NOTHING beats NOS anymore. Personally, I'd be willing to pay $100 or so for one so it'd be the last time having to do the job and it would work right. Did you check www.arizonaparts.com ? Good source also.

I quickly pulled this one up. Not sure it's right for your application and it was just a quick search so there may be cheaper ones!!! https://www.ebay.com/itm/284539431334? NOS Mopar 73-79 A,B,C,E-Body Turn Signal Switch 3488804 Again, I don't trust Standard, Dorman, or any of those others anymore. It's sad but that's the way it is now.

That NOS part isn't really much more than the TW7 mentioned.

Problem with NOS plastics that are supposed to flex, like the turn signal switch, is that they outgas and get brittle, even sitting on the shelf.

Flip a coin on which is better anymore.