Hello Bjorn! Welcome to the fourms - all the way from Knoxville Iowa.
I understand your hesitation when it comes to knowingly becoming a new owner of what Kubota refers to as its gray market models. Kubota really instills the fear and wrath of God on those owners that are considering purchasing these models or already have them and are looking for parts and support. They list the gray market models on their website and generally make it sound like those tractors are:
1) from another planet
2) a result of poor workmanship and materials
3) likely to explode the moment you sit on and use the tractor
4) after said explosion - no parts will be available unless you fly to and pick them up from Japan directly at huge expense and hassle
Of course, none of these are true and as much as I am sure Kubota does not like to admit it - these tractors are still Kubota designed and Kubota made. They are Kubotas!
I get where Kubota is coming from - yes, technically roll bars might be missing and so on, but I suspect the reason they might be a little hostile toward gray market imports is because it cannibalizes the sales of new equipment. A new 18 horsepower Kubota costs at least double what you might be able to pick up a good used gray market model for. They do not want you going down the street and buy that used 20 year old Kubota, which is still running strong and on its 3rd owner already - they want to sell you new equipment (hopefully as often as possible). No surpises here! They are a business and out to make their shareholders see a positive return, not to run a charity.
Bottom line: owning a gray market Kubota is not problem. If you equip yourself with some knowledge ownership of these tractors is no more of hassle than any other. You will need a parts manual, either an original written in Japanese (don't worry), or an equivalent manual for the Kubota model closest to yours. You will also need to get in the habit of not telling your local dealer that you have gray model. I have a hunch that dealers do want to help you and sell you a new part, but if you directly tell them that you have a gray model, they are caught in a tough spot - their dealership and franchise license requires them to treat owners of gray market models like jerks, so they will have to refuse you service on their own equipment!
My personal opinion on the matter - I think in the long term, Kubota will regret their decision to treat owners of these models so poorly. I think it hurts their brand and the respect of the owners of these models when they are cast out. If you owned a gray market Kubota and received such horrible service from them when you needed support, would you ever buy a Kubota again, new or used? Not likely. That green tractor over there is looking pretty good and they help me!
Ok ok ok ok, rant over!
Anyway - back to the task at hand - how many hours and what kind of shape is that L1-20 you are looking at in? Does it come with a loader or any other goodies?