Lapras is good, but you don't really need one. If you really want one, there is an event going on that makes Gigantamax Lapras more common in raids, but only for Shield players. You can try to join a raid with a Shield player that's hosting one and hope you get it, but its catch rate is abysmal. You can also try to get lucky with a Surprise Trade, or keep fishing. Overall though, while it's a very useful Pokemon, you don't need one. I personally would use a Barraskewda as a substitute. It's very fast and it hits incredibly hard. It's frail, but that doesn't matter when you can use Revives and have brute force on your side. Here's a Barraskewda set:
Barraskewda @ Life Orb / Expert Belt / anything else
Ability: Swift Swim
- Liquidation / Waterfall
- Close Combat
- Poison Jab
- Drill Run / Throat Chop / any other physical move
Hope I helped!