Looks like it's a 2-step process. First, let's figure out a number size for, say, the 29 waist.
Levi's says a 29 waist size is actually 29.5-30", and the seat is 35.5-36".
Then we want a converter. I went with this one:
So our Size 29 corresponds, more or less, to a US/Canadian women's 10 or a 12. This would convert to a size 12 or 14 in the UK, and a size 40 or 42 in Europe (and size 11 or 13 in Japan). The number isn't exact because a woman's size 10 in America is waist 28", hip 39"; and size 12 in the US is waist 30", hip 41".
Now let's try the 33
Levi's says: 33.5-34" waist; 39.5-40" seat
Converter says: size 16 American (I am using the dress table, as the clothing table on that site doesn't go past 14 American and this is clearly going to be just a smidge larger)
UK size 18
Europe size 46
Italy size 50
Australia size 20
Japan size 19
It is confusing and I am not certain it is right. Frankly, I would suggest buying a sample in each size and have female friends of yours who know their sizes try them on. Anyone who gets a pair of shorts that fit can keep them.
PS I also found this page which might be better: