There is alby which does Lightning Payments through the browser. (www.getalby.com)

There is nos2x which is created by Fiatjaf (creator of Nostr), extremely lightweight and does the job, been told it's decent for multiple user logins but don't hold me to that!

And then there is Nostore which is a iPad/MacOS extension. Sadly Safari only, but then again nothing else exists on phone or tablet to fill that void.

There is supposedly a Android extension/app coming out which holds your key for you and acts sort of like a gateway for Nostr clients.

Oh, and there is this.

(from https://github.com/nostr-protocol/nips/blob/master/07.md )