A year ago if you were going to P2F on a 737 you would most likely have ended up at Lion Air in Indonesia. I am happy to say that it is no longer possible as the government finally put an end to it so as to give locals a better chance. For the Indonesian authorities to allow a foreigner to work for Lion Air you now require 250 hours on type!
You say you have 250hrs on a 737 and as one of their recruitment (if you can call P2F recruitment) streams is now gone it may be worth getting in touch with them. Will not be great terms but better than paying.