I bought my Coyle Worldcon version (resin) when, no kidding, I had $20.19 balance in my Paypal account. Total coincidence.
I think what we may be missing that is so much of BR's production design and set dressing used old stuff. The "blaster" (I always thought of it as his sidearm) is a kinda Asian cheap-o firearm with plastic grip, the add-on breach gives it an "old tech" look. What's it do? Who knows. But instead of some electronics or caseless ammo or other sci-fi mumbo jumbo, it looks like someone cross-bred two firearms, retrofitted some electronics (much of the BR production design was based on retrofitting stuff onto stuff onto stuff to an insane degree), and voila, you have some kind of pretty dang powerful sidearm, maybe a one of a kind.
I have an old Webley that someone modded to handle .45 rounds (but takes cowboy load, my father said it "spewed metal" when he used regular cartridges), then did a botched job rebluing it. It's a Frankengun. Still firing, I should take it to a range sometime. That's what Deckard's gun reminded me of. Something a gunsmith toyed around with. He took it to a back-street Chinatown gunsmith who said, "They no make parts for these no more. But I can cut up this rifle I have in my trash bin and make something work for you…"
K's looks like something you'd buy. Or get from the armory. Or order from the back of Soldier of Fortune. I'm sure it serves the plot. I'm sure it even fits the character (Deckard was "out," maybe K is still on active service). It doesn't have to look like Deckard's, probably better that it doesn't to help differentiate the characters and their kit. All this poo-pooing, you'd think they gave Deckard a different gun that looks like the Star Trek Discovery Phaser 2.