If you searched plans for building a completely new compressor, you should have told it right away. You may be able to find some plans on the Internet, but unless you have access to extensive park of metal working machines, and have great experience in construction, working, and assembling of high pressure devices (what you apparently do not have), then you have practically no chance. And even if you had all that experience, access to metal working machines, and managed to manufacture or buy all the high pressure components, seals, filters and other parts needed for the new compressor, I doubt you would manage doing it cheaper than buying the compressor from a store. More likely, you would spend several months or years of free time on it, and pay multiple times the cost of what you would pay for a new compressor. And also quite likely you would die quite soon afterward as a result of a high pressure explosion.
That is really not worth of the hassle and risk. If you need to have your own compressor, you better save some money and buy a new or used one. New quality scuba certified compressors start at around $2000, and you can probably get a cheaper used one too. Without the motor it can be a couple of bucks cheaper, but since the motor is the cheapest part, likely it won't make any big difference.