Color me surprised. Maybe you received The Bug Letter.
Maybe you’ll have to approach this old-school and work your way up from small works, small colleges, small orchestras. The road to the peak is rocky, but take heart, as Randy Newman says, “It’s Lonely at the Top.”
“Grovel” is right. And I would if I thought it’d get me somewhere.
But the biggest gorilla in all this is the perception that if I paid for this it would cheapen the value of the composition, said value real or imagined. The perception upon learning the composer paid big $$$'s for the performance would be:
“Well, he had to pay to get it premiered so it can’t be that good.” An immediate negative connotation is created upon the listeners learning this. Only by having a sterling performance, mistake-free and one that would knock the listeners out of their seats could this stereotype be overcome, hence an even greater need to avoid 2nd and 3rd-class premiers.
That’s one hell of a catch 22 isn’t it? How do new composers get their break at all these days? Is this why fringe classical listeners like me haven’t really heard of anyone since Barber or so?
I think you should really consider the Eastern Europe idea - highly skilled musicians at a much lower rate. Make it a month long vacation and you’ll well adjusted by the time of the performance.
Better, just up and move there for a year.
How do they get their breaks? In two words, “they don’t”, especially when they are writing giant difficult piano concertos that require a top-tier pianist and top-tier orchestra to perform them adequately. That was my first mistake, but I wrote it to fulfill a dream I had as a young piano student in love with Rachmaninoff’s 2nd Concerto (still am) to write a piano concerto and premiere it as soloist with our local symphony orchestra. I only got as far as the 1st movement and it was trash so I shelved it.
Back then things were very different. Classical music was as politicized as it is today. It’s big business full of huge egos and landmines and if you don’t write exactly the way they want you too (I don’t, being a neo-Romanticist) they you don’t get any support and are actually laughed out of the rehearsal if your music has anything resembling a hummable melody—melody is anathema to the music apparatchik these days).
If a composer wants a shot at establishing himself his best bet is to write for 2-3 players, the largest ensemble should not exceed maybe 10. The (s)he can get a group of student-friends together to give a premiere. But a half-hour unknown concerto by an unknown composer that needs an orchestra of 90-100 players to make it sound good plus a pianist of extraordinary technical powers is a ticket to nowheresville. 
Edit: classical music wasn’t as politicized as it is today.
Edit: then you don’t get any support