Cold Trap - The how's and where's question

Hi all,

Newbie to this great forum with a vapor trap question.  I have distilled nitric acid several times recently - both using my vacuum pump and without.  I really like the vacuum distillation method but want to perfect this technique with the inclusion of a vapor cold trap.  

  I use a Gast vacuum pump - a great lab equipment that was bought used for $20,  and do not want to damage the pump when used and  being exposed to vapors.  There is almost nothing about cold trap / vapor traps on the Tube or elsewhere for information on the subject.  I've found items on ebay that sell from hundreds to as small as twenty dollars, but do not know enough about the items to make an informed purchase.

Education on the subject will be appreciated.

Regards.

Gray