A
Yes, there is. Use the following method:
Get an Adamant Smeargle, preferably a high-level one.
Get a Staryu with Reflect Type, get a wild Smeargle to copy it, and copy it off of the Smeargle with your one.
Teach it Sketch again at the move relearner.
Get a Sylveon with Skill Swap and get a wild Smeargle to copy it, and copy it off of the Smeargle with your one.
Teach Smeargle False Swipe and a good powerful move against Beldum with the above method. Single target only, no Normal or Fighting-types.
Breed a male Reuniclus line Pokemon with Skill Swap with a female Ralts line Pokemon so you have a Ralts with Skill Swap and Synchronize, which you train up.
Get a Pokemon with Trick-or-Treat, Gourgeist probably.
Now we chain:
Trick-or-Treat Beldum with Gourgeist.
Skill Swap it Synchronize with Gardevoir.
Then you send in Smeargle who Reflects Type to become a Ghost-type then Skill Swaps to grab Synchronize.
Get Beldum to call a friend with Adrenaline Orb.
KO the Ghost-type Beldum, then chain with False swipe, switching Beldum after 15 turns each so it doesn't struggle after the 20th move
This works with Jangmo-o, Bewear and Riolu too, but they have different lengths of turns. The call rate is also different, and after a 255 long chain, there is only a 18% chance of a shiny throughout the whole thing. This is a long process, so get a lot of Leppa Berries. Synchronize still works despite swapping, but this is after 3 tests, of which an Adamant Smeargle has drawn 2 shiny Adamant Riolu.