The trick might be some hi-low shopping. You know...like the Leith pants, which really revitalized your spring looks. For only a few dollars.
But I see a danger, too -- because this kind of jacket won't work with something like those pants. And then we get into all the troubles with proportions. Ugh.
So ultimately, at least as a beginning, I think you're spot on -- you need to find "your" brand. The brand that both gets your body AND is neither too "out there" trendy nor too staid and frumpalicious.
Because there are two ways of going "modern classic." One is to take classics like this and modernize them with other items/ accessories/ etc. That is totally do-able, probably economical (to those who get it...due to possibilities for thrifting said classics, as Ingunn does) but also quite complex and you really need to have an eye (and time on your hands).
The other way is to get it from the designer him or herself. Holus bolus. Go for a designer that just does "modern classic" vs. classic.
I do think your body type gives you options that many in your situation might not have. You have a lithe figure and can wear lots of silhouettes. Yes, it's true, fitting pants can be a pain (but that's true for most of us). It does occur to me that the brand that "gets" your body might differ for top and bottom.
I wonder if Angie or Inge might have ideas here. Maybe if you post a thread for brand suggestions for slender body type, woman-of-a-certain age (i.e. over 40). And then I will eagerly read along!
Vince Camuto comes to mind as a lower priced option, but I do think the sizing is on the very generous side and might not work across the board for you. And the fabrications are sometimes less than one might dream of.