In my local reefers FB group the local petco guys post occasionally. They take orders, let people know about overstocks, sales etc. With any luck maybe you could get to know the guy who runs your local fish dept...
That would be worth a try but, IME, it's really going to depend on the Petco and the Fish Manager at that store.
I used to have 2 Petcos within 15 minutes of my house. One was hit or miss with SW livestock and would not take orders for livestock. The other had a great Fish Manager and had great (healthy, wide variety) SW livestock and would take orders. Unfortunately, they closed both those locations and consolidated them into a (new) location geographically located between the two former locations. Since then, quality, variety, and availability of SW livestock is hit or miss and they will not take orders.
Another Petco about 30 minutes from my house has an incredible SW livestock selection and will order livestock for you. I've spoken to the Fish Manager at that location and she told me that corporate dictates how much and how (take orders) each location will receive based on sales. In fact, this location also has a dedicated frag tank with SPS, LPS and Tridacna always available.
So, a location that has low SW sales only gets a limited amount of SW livestock/cannot take orders, while a location that has high SW sales gets essentially whatever livestock they want and can take orders. This seems a bit strange to me because, if you increase availability/variety of livestock, you should see an increase of sales at that store. If you restrict availability/variety, you're not going to get a lot of sales.
For example, the Petco close to me with hit or miss livestock regularly has Damsels, Clowns, Pseudochromis and the occasional Royal Gramma. Once is a blue moon, I'll see a Tang or two, maybe a leather coral frag or two, and on very rare occasions I've seen anemones and T. Derasa. If this store would have a greater variety/quality of livestock, I'd be buying there all the time.