6n12a-2d Equivalent 6v dry cell?

I've got a 1978 Honda Twinstar project. The dead battery in the bike is a 6volt 6n12a-2d lead acid and I want to go with a small dry cell under-cafe-seat option with electric start and led lights.

Can someone recommend a dry cell that would work well in a cafe project that won't have much hiding space? And is there anything else I'd need to swap out for charging it or other considerations?

Not sure about AGM, but Shorai makes a 6V LI-ION battery.

LFX18L2-BS06

Check voltage output on your charging system before swapping to LI-ION, though. Anything over 7.3 and it's probably best to stick to lead acid and/or swap out to a newer 6V regulator/rectifier.

Thanks Sonreir, checked it out, did more research, went with the LFX18L2-BS06 you recommended.