You're a bit out of our mid-Continent North American operating area, but for what it's worth...
Have had excellent results with Baldwin brand filters; run them on all automotive and eqpt for which they have a match.
Baldwin is international. Try their website and email a TechRep for a crossover model number you might find more locally. Be prepared to tell them the engine model and sub-specification number if you know it and also current filter OEM part number.
Donaldson is another aftermarket brand you can try finding. They supposedly make the Kohler line of filters along with others under different names.
As for oil level, do you mean the engine has no original dip stick? Industrial engines I've been around without sticks are all "fill to overflow", e.g., some Waukeshas (also found on old pushmowers), or have a sightglass of some sort. Use this at your discretion as too much is probably as bad as too little.