Normally, I'm very much live and let live when it comes to poker chips. Use what you can afford and be happy with it. I will say that I would do whatever I could to strongly warn people from purchasing these. Personally, I found them barely functional for their purpose. Sure any round plastic disc can serve as a game token. But my experience is they did not stack. They just kept falling over and made a general mess. Nearly impossible to handle. They were tremendously frustrating to use for me. I would encourage anyone that could afford even slightly better to get dice chips or whatever. I would prefer playing with the actual cash and coin to these.
An answer to the OP's initial question I cannot think of any mechanical intervention to make them less slippery that wouldn't involved compromising the basic chip.