Consider:
a) let Google find you a list of pieces for organ and trumpet

b) then decide which pieces you might want to perform in concert and practice the trumpet part.

c) recruit an organist, - if necessary through the Boston chapter of the
American Guild of Organists - interested in playing with you in concert.

d) with or without the organist's collaboration identify churches with a good organ

e) negotiate with one or more churches for concert time. Find out how much if anything they will charge you. Offer as quid pro quo to accompany their hymns at Sunday services with the trumpet. 

f) either sell tickets for your concert or after the concert, or both, solicit donations to the Camelot Music Society Trust. Split net ticket receipts, if any, with your organist. Pay as much as half of any donations to your organist partner. Set aside the other half of the donations in a separate (perhaps only virtual) account remaining in and belonging to the Trust from which payments in appropriate amounts will remain payable to you.  Prior to your first State and Federal Reports for the Trust, pay yourself $10.00 and inform the State and Federal authorities that absent objections from them, you will compensate yourself out of your virtual account at the 50% median rate for trumpet concert performers. If they object, return the ten dollars and appeal their ruling. If they don't object, you have a precedent on which you can rely to justify further payments.