I want to use patented technology in my product

IP law is not just patents. IP also includes trade secrets, copyright and trademarks. Trade secrets are an odd beast. The rules are much more vague and you can only claim it if you keep the secret. There are ways to share a trade secret such as NDAs. There is nothing preventing you from reverse engineering a product that is only protected my a trade secret, provided you do it from a public information or a copy of a product you legally bought (in other words, no seeking into their factory and steeling their plans).

If you do not see the patent numbers on the device, packaging or their website, ask them what patents they claim on the product in which you are interested. You can also search for the companies patent's on google patents or the USPTO's website. Although, not every company attaches their name to their patents, but the investors must have their names on the patents.

What part of they own the patent do you not understand? Pay what they want for their product or go without. Reverse engineering is theft. How would you feel if you were the patent owner and someone stole your product?

At least I'm not aware of any reason that would make it illegal for you to reverse-engineer their (or any) technology, as long as you don't use (such reverse-engineered) technology that is patent-protected, in sold products or the production process in an area where their (potential) patent applies. That restriction, however, may prevent your local manufacturer from spending time in that process, because they could not exploit what they learn for some time. But it's never wrong to talk to them, I guess. If your finished product absolutely requires this (patent-protected) compressor, you're at their mercy: they can forbid you to use their compressor, and you need to assess whether this would ruin your business model.