This story was in a collection from the early 1980s that I think contained only stories of alien encounters from various authors.
In this story, set in the near future, the protagonist is an ex-congressman who lost re-election and returns to his family's junkyard, maybe in New Jersey. I remember his name being Pierce Sansoni or something close to that. He visits a neighboring junk dealer who claims he has 20 of some kind of machine or equipment. One canister is open and contains the expected item. The protagonist buys 10 of the canisters and returns home.
His father reminds him to "keep the stock UP!" and sends him back to buy the other 10 canisters the next day. After being stopped due to a single car wreck with a missing driver, he gets to the neighboring junk dealer's yard to find it destroyed and the man dead. As he returns home, a spaceship descends and wrecks his vehicle and he wakes up in the alien ship. He is held in an oxygen filled plastic bubble epoxied to a corner of the control room. There is a woman also being held in the bubble - she is the driver from the wrecked car. There are four insect-like aliens who use pictures to show him that they are looking for the remaining 10 canisters. The two humans are able to escape and steal a car to return to the family junkyard.
The next morning the father, the protagonist and his brother set a trap for the aliens using the canisters as bait. When the aliens arrive, the humans have a welded cage over the canisters that takes all four aliens to remove. This gets them all out of the ship and the humans open fire using a variety of weapons. Once the aliens are killed, the father is able to open one of the canisters to review a totally human looking alien in suspended animation. The alien wakes two more of his people who then recover the remaining 7 canisters and leave in the ship (which belonged to them all along). The junk dealing father keeps the three canisters that the woken aliens came from, reminding his son again to "keep the stock UP!".
Two other details: the insect-like aliens are called something like Wheescricks and the human aliens say a phrase that sounds something like "sally constantine".
I think I remember these details fairly accurately, but the name of the story, book and author escape me and I would really like to read this again. Any help is very much appreciated!