I bought this universal diffuser from Amazon, and it's great! https://www.amazon.com/Hairizone-Universal-Diffuser-Adaptable-D-1-7-Inch/dp/B01N05UG34/ref=sr_1_1_sspa?ie=UTF8&qid=1516668635&sr=8-1-spons&keywords=universal+diffuser&psc=1
I have a pretty good hairdryer with 3 levels of heat and a cold air button, and when the diffusing attachment that came with it broke, I bought a universal attachment from Amazon. After having seen that at my hair dresser's the diffuser attachment is more a kind of bowl (as opposed to the flat one with spikes I had before), I shopped specifically for that. This is what I bought, it holds reasonably well.
I mainly diffused to speed up drying time, so I’m not sure it makes much of a difference for me. I used an attachment from Amazon: https://www.amazon.com/Hairizone-Universal-Diffuser-Adaptable-D-1-7-Inch/dp/B01N05UG34
I use this one. Universal and sturdy. Occasionally falls off the hairdryer, but otherwise great
I found this one on amazon and it’s great! Hairizone Universal Hair Diffuser Adaptable for Blow Dryers with D-1.7-Inch to 2.6-Inch for Curly or Wavy Hair, Shiny Black https://www.amazon.com/dp/B01N05UG34/ref=cm_sw_r_cp_api_i_2ygiFbXPTJJKC
I forgot to mention about diffusing! You can use a hairdryer with either a diffusor attachment, or you can get a diffuser bonnet
Otherwise, you can let your hair air dry :)