I've been using this funnel to fill mine up under the cabinet, works really well. Just be careful not to overfill since you can't really see the level....I usually just listen for the water no longer splashing and stop there
I overflowed once and it was a pain to clean, luckily doesn't seem any damage done
I use this since my Lelit is under some cabinets.
ALWAYS look on Amazon.
https://www.amazon.com/Lisle-17232-Right-Angle-Funnel/dp/B00MEPIU4M/ref=sr_1_17?ie=UTF8&qid=1547765096&sr=8-17&keywords=oil+funnel
Identical funnel $7