Although two expansion packs have been released for Pokemon Sword & Shield, The Pokemon Company still managed to leave out a large number of Pokemon from the National Pokedex. You can go to the PKMBuy website to buy Shiny Pokemon you want. When the game was first released, it stirred up controversy because it was the first time that the entire list of Pokemon could not be accessed in the mainline entry. 

Slaking
Slaking goes for to be the most important troll design that Pokemon Company has ever attracted audiences. It is a Pokémon with higher basic attributes versus the pseudo-legendary Pokémon, nonetheless, it can play truant, so that it cannot attack continuously.

Fans have realized that pairing it using a Pokemon that could offset or exchange abilities within a dual battle allows Slaking to shine and reach its full potential. Since the Pokemon Sword and Shield will not have many double battles away from competitive games, it's wise why it was never added.

 Kalos Starters
Pokemon X & Y is considered by many for being the low point from the mainline game in the series. The Pokedex in the Kalos area is pretty small, it has added dozens of Pokemon in the entire national Pokedex. 
 
Despite this, people still like some starters, as the water-type Greninja has become one of the most popular Pokemon from the entire series. It plays the top role from the movie Detective Pikachu, nevertheless for some reason, about Pokemon Sword and Shield, it seems to get an afterthought.

Zebstrika
Although zebras are almost horse-like animals with strange colors, they have got become a significant part of popular culture because of their appearance in lots of animated films. Zebstrika is undoubtedly an electric zebra on the giant Unova area, called the Thunderbolt Pokémon.

In several ways, it's a version in the fifth-generation Rapidash, but they also decided to base it around the zebra and earn it a new type. Its basic physical attack data joined with above-average speed helps it be a real threat in combat, unfortunately, novices cannot experience it for themselves in Pokemon Sword & Shield.

Toucannon
Let a whole generation of kids have been familiar with toucans, thanks in large part to Froot Loops ads. When a Pokemon inspired by toucan was released as part of Pokemon Sun and Moon, fans were enraged. 
 
Toucannon, or Cannon Pokemon, is a normal/flying type, somehow similar to your final form with the woodpecker's basic Pokemon. Buy Shiny Pokemon is the new player's choice. Most Alolan Island Pokemon may be used in Pokemon Sword and Shield, nevertheless, for some reason, this huge cute bird that has a gradient beak was excluded.