Well here you have it . . .
Put your Spanx on.
Go down to a Chinese restaurant and get some MSG as
AMN suggested.
Once you get home mix up
Sandy & Holly's "cocktail" of magnesium citrate 1/2 cherry flavored 1/2 lemon lime flavored with a touch of Miralax.
Do 1 suppository as suggested by
DM. Follow up with 1/2 dose of Benefibre as
Lady suggested.
Once you have done that mix 4 caps of fish oil and 1/4 cup of olive oil with 16 oz. of
RW's great recipe for Irish Creme (trust me you will need the sedation - you might want to add a 5 mg tablet of Valium for added relaxation) and then follow up with
FG's Dulcolax.
By following these steps before you fly, you should clear out at 30,000 feet in the air.

On a serious note, I am sorry about what the 'roids are doing to you. I have experienced that from steroids but definitely from having a neurogenic bowel and bladder.
When I flew back east last year one of my sisters gave me a couple of prunes. While they did not work right away, they did work. Thankfully, we had landed and were waiting for DBF to come pick us up at the airport.
Wishing you luck!