Closest cross in the U.S. is Citgo Cylinder oil 400.
P66 and Chevron have ISO 460s. But that product you have crossed to approximately an ISO 320.
5 gallon buckets would be the smallest packaging.
Non-synthetic worm gear oils / steam cylinder oils / cylinder oils either still use Tallow as a friction modifier, or an artificial tallow. So you can’t / shouldn’t use regular gear oils with EP additives in it. Worm gears need protection against sliding.
In a small bottle, we could look at some PAG stuff. Maybe HPL has something, I’m not sure, in a small bottle.
Otherwise Citgo and others make a PAG 320 that would work. Their worm gear oils but it’s… exotic. Again, 5 gallon bucket is probably the smallest packaging size.
Otherwise, light load? Find some R&O 320 maybe.