ghetto style... put the gun in a sack so the cops can't find the evidence
I got nothing on an attached catcher. I tried that on my AR for a while, but it was in my way, and a shotgun would need a larger thing. The hulls are often magnetic, so you can maybe exploit that somehow, but at the end of the day you need some kind of net at the ejection that leads to a storage container.
you can also just use some kind of bright, awful color that you can see amidst the regular clutter of black, red, green.
I should be possible to make up a shell catcher from heavy cloth or even netting by using extended assembly pins to mount a catcher under the ejection port.
Steel, aluminum, or possibly even plastic could be used to make up new pins with holes in the ends.
Cord could be threaded through the holes and used to hold a catcher under the gun, which would also hold the pins in the gun.
If you wanted to get fancier, you could use clevis pins and Kydex to make a box type catcher that could be quickly disconnected to empty.
The problem is, most any shell catcher is going to seriously interfere with loading, since the gun loads and ejects out the same area.
I suppose if enough thought is done, a pivoting box could be designed that could be tilted out of the way to empty and allow loading without removal.
Due to the design of the Kel-Tec's, having shells fall to the ground is inherent to the design, and any shell catcher is going to pretty much eliminate any kind of viable shell catcher that will also allow easy or fast reloading.
What am I not getting about our bottom eject shotguns?
Maybe get a horses feed bag, and adapt it with duct tape?
Call Frederick's of Hollywood, get a set of fishnets that clip on garter style, and hang 'em from the receiver?
Stand on a tarp while shooting?
Use a strong magnet and stout line to fish 'em out of the grass... and a lawnmower to get the grass to reasonable length.
Coat the bottoms of the shells with just a wee bit of Cavorite.
All you need is a slightly longer front pin for the trigger group that has a couple of holes of wire clips to hold the front of the bag that catches the shells. You can tie the back up to the angle brace of the buttstock. The bag can be made of anything hot hulls that won't melt. Cotton fish net would be my choice so I tell how full the bag was.
"It's not the size of the dog in the fight, it's the size of the fight in the dog." - Mark Twain
Received it from Custom Cast (quick shipment from Etsy order), installation was easy, works like a charm. Seems well-enough built, although time will tell. It will make reloading a bit slower, as removal and re-attachment, while quick, isn't instant. However, depending on what you're doing that is either a show-stopper (e.g., high round-count 3-gun / multi-gun) or a non-issue (e.g. range time).