Less than a week ago, my company threw away ten or more 486 and Pentium (<150MHz) PCs.
I assume your requested systems are needed for some special legacy application. Do you have any other requirements? Such as:
Do they need to be EXACTLY a 40 MHz 386-based system, or is anything over that acceptable? (486DX2/66, 75MHz Pentium?)
If you need multiple units, do they need to be identical?
Does a tower or desktop matter?
Any RAM size requirement?
Is a hard drive needed?
Do you need several serial ports?
Do you need full-length ISA slots for a particular interface card?
There are no Ram requirements, no HD is fine. The requirements would be 386 or 486, with 3 parallel ports. They don't need to be identical, and any working systems will pretty much do.
The systems are used for an old lighting system, crown lights, scrolling marquee etc.