Yugster.com is offering combination trigger locks. They look like they're the same as a similar model on Amazon.com that's $10-12. These are $6. I bought 5 because I hate dealing with keys. Previously, I bought two identical sets of trigger locks that came in a bundle of 5 that were all keyed the same I ended up with 5 with one key and 5 with another key...grrr.
https://www.yugster.com/deals/71110-gun-trigger-lock-with-3-digit-combination-by-outdoor-nation
$12 at Amazon: http://smile.amazon.com/Lock-Outdoor-Nation-3-Digit-Combination/dp/B0147C7HZM/ref=sr_1_1?ie=UTF8&qid=1460071726&sr=8-1&keywords=combination+trigger+lock+outdoor+nation
https://www.yugster.com/deals/71110-gun-trigger-lock-with-3-digit-combination-by-outdoor-nation
$12 at Amazon: http://smile.amazon.com/Lock-Outdoor-Nation-3-Digit-Combination/dp/B0147C7HZM/ref=sr_1_1?ie=UTF8&qid=1460071726&sr=8-1&keywords=combination+trigger+lock+outdoor+nation