I haven't found anywhere with a good list. I am picking up odd info up here and there and observing the deposits left on the fleece as well. Rusty and Peanut are calcium markers in more ways than one! My vet gave me a list of veg which is copied from Rabbit Health News 1994 Vol.11, P7 -author John E. Harkness. It's a little helpful but not completely as the things it lists to feed daily just about all give my piggies sludge. I also lost belief in it when I got to the list of treats only small amounts - coriander and the list good choices - cilantro, this is the same thing so which is it? It lists dandelion as 103mg, I assume per kilo but it doesn't say that. It gives sweet peppers as 6mg, loose leaf lettuce 38mg if that helps see how high 103mg is. There's a list of things not to feed or only very occasionally in small amounts which includes clover, goosegrass, sowthistle, spearthistle and sheperd's purse but with no actual calcium amount.
The vets have also told me that it's one thing to reduce the calcium if feeding a high calcium diet but going too low can also cause stones as calcium will be stripped from the bones and also cause other problems later in life. A diet too rich in oxalates will also cause stones so foods such as spinach, celery, parsley and strawberry should be limited. The whole diet thing can just become a minefield the more you look into it. Another reason why I now feed a small bit of a variety of foods and keep an eye on the fleece.