I use an Omron MicroAir:
https://omronhealthcare.com/products/microair-nebulizer-neu22v/
It is available through many retailors, many of whom have quick and free delivery. In the USA, you need a prescription to purchase it. Because it is ultrasonic there are some medications it cannot be used for (most of them are related to CF treatment, but there may be some used for other purposes).
Pari makes a very nice portable nebulizer:
http://www.pari.com/us-en/products/compressors/trekR-s-portable-aerosol-system/ . You need an Rx for it, too, in the USA.
Personally, my choice would be the Omron or the Pari; both are well-regarded and tested; the Pari more so. I use the Omron because I started using the previous model of it before Pari came out with their portable model, and it is really portable, otherwise I would have been using a Pari

I have a larger Pari at home.
Speak with your MD about whether a nebulizer is appropriate and if so which one(s) they recommend and why. note they may not be familiar with the portable ones -- my MD was not and I had to educate him about them.
SW