i've been seeing this video posted around various threads over time, and it's the same kind of effect that you're looking for, without having to purchase anything
even if you've got compression only on your jugular alone, whenever the blood pressure buildup in your head reaches a point when you can no longer take it and want to pull back, do it. the pressure difference in between your head and body creates a large rush of blood from the head due to the buildup, and turns you unconscious in seconds. think about it in the same sort of way as getting up from a seat/bed too quickly; you're lightheaded and have darkened vision for a few seconds, until the optimum balance is reached again and your back to normal functionality. this is the same thing, but to the extent that it makes you unconscious, at which point you've got yourself the same effect that something like chloroform would do in a hanging.
i haven't tried any of this out myself, i'm not at that point yet, but the video does a really good representation of the sihpon-unconsciousness effect. sort of ironic how the original intention of it was to prevent deaths by the method, but because it's such a sudden and painless occurrence, people are going to it to learn how to die