Get the best u-lock you can afford and replace any quick releases with skewer locks and pit locks. Learn how to lock your bike properly as well, and don't leave it out for too long.
I personally recommend: Abus U-Lock - Granit X-Plus 54 Key, 5.5", Black https://www.amazon.com/dp/B00GCB287O/ref=cm_sw_r_cp_api_M6BwzbCB8B4K6
I live in San Francisco, and bike theft runs rampant here. I use two abus u-locks and skewer locks all the time. Thieves will go after the easiest target.
Just fyi, cable locks are pretty useless--you're basically using a shoelace to prevent a thief from stealing your components.
They sell them in amazon.
However chains are only meant for on-site locking. If you’ll be riding around, you probably wanna get the Abus granit and a long shackle lock I prefer the Onguard Brute LS 8001 or Kryptonite NY LS( a guy in Kijiji selling it for $90)
With locks and chains it is not just the brand, those OnGuard were made to be sold at WalMart to protect retail bikes. But something like the OnGuard Brute is sold in ebike shops and designed for locking ebikes/motos.
I personally wouldn't lock a Rad or Lectric XP with the WalMart ones but that is just me. If you live in a small town, or a really low crime rate city they could/would do fine.
I can't afford to have my bike stolen as it is my daily commuter so went for the overkill route with the items listed below.
Schlage 12mm Cinch Ring Security Chain
I can't afford to have my escooter or ebike stolen, as I daily commute on both for summer/winter so went for the overkill route with the items listed below.
Schlage 12mm Cinch Ring Security Chain
Lock, ABUS U-Lock Granit X-Plus 540
Main chain, Schlage 12mm Noose Security Chain
Cable loop, Schlage Flexible 3/8" Steel Looped Security Cable
Cover, TeamObsidian Bike Cover
I always cover my bike well parked and loop the cable through the cover, chain, and front wheel. Well the cover does draw attention, it is overall less than my heavily geared RipCurrent would alone without cover.