Having a real struggle finding some softshell troos which come in 28/32. Have had base jumps in euro 22 which were ok fitting, but I've not been convinced by the quality/lifespan. The usual makes in size small always seem really baggy which I find really annoying for climbing in.
The only thing I'd say is that their sizes seem quite generous. 28" waist, 33" leg on Mammut is a Euro size 90. I found them a little too wide and the legs seemed as long as my other trousers that are 34"
I'd go to a shop that has the 86 and 90 sizes available for you to try.