First thing to do would be to check your wiring. A common cause of humming from chimes and power failures is not installing the power module that came with your doorbell.
See here for instructions: How to Install an Alarm.com VDB770
Here is a diagram:
If your wiring is correct and the chime is still humming, is there any chance you can just rely on the panel to make the chime sound? The IQ 2 and 4 both get pretty loud for doorbell rings. I personally set the doorbell volume to maximum in my settings and it is louder than any mechanical chime I’ve ever had.
If so, you can unwire the chime altogether and just put a resistor in its place — again, explained in the link above. The resistors can be ordered for less than $10 on Amazon or for even less at Home Depot / electrician supply stores.
Here’s a diagram for that:
If you absolutely have to replace the transformer, the 770 actually works with most off the shelf doorbell transformers. No specialty transformer is needed. Just make sure that it’s a minimum voltage of 16 VAC and minimum power of 10 VA. Any doorbell transformer at the hardware store that meets those minimum requirements should work.