Look for platinum cure or medical grade silicone, glass, or stainless steel. Avoid TPE and PVC at all costs.

And shop online. Your local sex store worker likely doesn't know very much about the individual products, and will tell you whatever you want to hear. Any product listing on a website will absolutely divulge every secret there is to know about it, and beg me for the privilege of my purchase. If you absolutely want to buy in person, go after you've looked up the product online.