Hi Nick,

The best option is a small USB interface with two mic inputs. Make sure at least one of the mic inputs offers a 'high impedance' mode and you'll be able to plug your guitar into that. The most popular option is probably the Focusrite Scarlett 2i2, but many other manufacturers make something similar. The SSL 2 and 2+ are also good and have lots of gain on the mic input so you can use it with quiet mics like an SM58.

If you want it to sound good over Zoom it's a easier to wear headphones rather than using speakers. Otherwise the Zoom sound can end up being rebroadcast over the speakers and picked up again by the mic, unless you have things set up just so.

Where are you based? I may be able to dig up something suitable next time I'm in the studio.