I for one have not found an ideal replacement yet, so am reverting to a portable compressor model, the InnoSpire Go, which has been my go-to for probably close to 10 years.
Philips was having sourcing issues with their parts, and some people experienced leaking from the nebulizer head.
As for finding a hand-held (mesh) replacement, since I must self-pay, my upper limit is $200-250. There is nothing there.
There are cheapies, sold on Amazon, with terrible track records. I do not believe they are meant for 2-3 times a day use over extended time.
There are also $80-150 dollar ones, but none of the heads can be sterilized to the standard needed for those of us at risk for MAC (they are reported to be "self-cleaning" with distilled water, or soaked in vinegar - no boiling.)
There is a $400 one, on the market in the UK, but I cannot find a US source.

Somebody, please find us a new one! I miss the convenience.
Sue