Virginia Knight asks:

>Any suggestions?

There are three wonderful concerti by Einojuhani Rautavaara recorded
on Ondine.  Also, if you are amenable to neoromanticism, there are two
concerti by Lowell Liebermann.  There are concertos by David Ott and (?)
Oldham.  I'm not sure if these satisfy the requirement for post '50s, but
there's the Barber concerto, several concertos by LaMontaine, concertos by
Lee Hoiby, John Carpenter, Peter Maxwell Davies, Michael Tippett, three
concertos by Merikanto, a concerto by Panufnik, ...

len.