Julien's Auctions has an original "nearly complete spacesuit" from 2001: A Space Odyssey up for auction. The starting bid is $50,000 and they expect it to go up to as high as $300,000. From the auction listing:
The spacesuit is an amalgamation of components worn by different actors and in many scenes throughout the film. This is highlighted by a helmet featuring four distinct layers of paint (a base of color of white, then green, then yellow, and lastly in its present color of white), indicating that it was used in different scenes by multiple actors and representing a number of characters . This nearly complete costume is of the lunar type in its present state (silver body suit, blue back pack, white helmet). This suit appears to be original in silver (never repainted). However, due to the layering of paint, the helmet appears to have been employed as a lunar type, then two of the four Discovery types (green and then yellow; the other colors/types being red and blue), then as a lunar type again. This helmet has a textured strip of tape inside with "HELMET A" written across in red.
Most notably, the base green layer of paint seen in chips, cracks, and green overspray throughout the helmet surface suggest that it may have been the very helmet worn by Keir Dullea, who portrayed Dr. Dave Bowman (the lead astronaut on the film's Discovery mission to Jupiter) in the sequence in which he reenters antechamber of the Discovery surrounded by banks of circuit breakers leading to the "brain room" and logic center to "kill" HAL in one of the most famous science fiction scenes of all time ("Stop Dave. Stop Dave. I am afraid. I am afraid Dave.").
$300,000 seems like a lot to be spending on a Halloween costume, but I'm all about authenticity. And yeah, maybe I went into crippling debt to get my Mr. Rogers costume just right last year, but I had the last laugh when my sweater was the perfect shade of red even though people just assumed I hadn't dressed up at all.
Keep going for one of the iconic scenes of the spacesuit in action.