Inverter EF1000iS appears to be the smallest "electrical power unit" currently marketed in the US as a "consumer product." It's rated at 1100 W. There are no generator products listed in the current US model line that are other than 4-cycle engines, and I think that's been the case for several years.

I find a few smaller units – down to 600 W – offered for sale (used) but all that I looked at are also 4-cycle.

It appears that all current US Yamaha models are "electrically governed" for engine speed control.

This site has a "parts and service" button that indicates that you can "view" owner manuals and parts catalogs, but offers only "buy" for the service manuals which you would likely need. You can "browse shop and maintenance items" but it doesn't say (without going deeper) whether you can get the shop items.

The parts and service section "recomends" that you register and log in, but it doesn't appear to be required. You do need to enter a specific model number for your machine in order to get into viewing the part lists. There is a caution that parts for older stuff may be unavailable, and they appear to say that you must buy parts through an "authorized Yamaha dealer."

If you can find a similar Yamaha site for your international region, you should find something similar. The US site is fairly "user friendly" although they don't go too deep into the details.

I've heard rumors that the use of 2-cycle stuff persisted a little longer outside the US, so you may even find some current stuff of that kind at the site for your region - if you can find it.

John