Good question. Personally, I like PurSources 20%. The cream is light and not greasy, and it absorbs quickly. It has a menthol scent, but it's not terrible; apparently the 40% is unscented, if you believe the comments on Amazon. Not too expensive, either. It also contains tea tree oil, which is known to have an anti-inflammatory effect; however, I don't know if the concentration is medically significant.

Eucerin is a great brand, but the only one with 30% urea, I believe, is Eucerin Rougness Relief Spot Treatment, which comes in a fairly 2.5oz small tube. The bigger lotion doesn't say what concentration, but the spot treatment says it's 3 times the urea concentration of the lotion, so most likely 10%.

Udderly Smooth has a 20% urea cream. I've not tried that one, but it's a popular American brand.

You can also get shampoos with 5% urea (Eucerin and SebaMed, for example), though the concentration isn't very strong, and you have to wait at least 5-10 minutes before rinsing to get any effect. But this could be good choice as general-purpose shampoo, in addition to the overnight descaling.

(For the record, I wrote the descaling guide.)