I would avoid using fertilizer that contains Urea on orchids. Short term use shouldn't hurt but long term usage exposes yourself to potential problems. Best to order a good fertilizer online if you can't find it locally.
The biggest down fall is that it (urea based N) isint as readily available to the plants. Urea has to be first broken down by beneficial fungi to release the N to the plants. These fungi are not living within bark based medias, as they are typically soil organisms.
There really isn't a problem here. There is no harm in your plants going without any fertilizer, until you can order some more. In fact, a few weeks without fertilizer may well help your plants set more buds. Take care, Eric
There is an equilibrium between urea and more useable forms of nitrogen even in the absence of the appropriate bacteria, so you can use urea if you want. Heck, for many many years people grew orchids just find with urea. You just need to use more of it, and a lot if it ends up on the floor.
Use the miracle grow until you can find a better fertilizer, at 1/4 the rate it says to use on the package. You'll be fine...