I use a KROWN mfg phone flasher.

I have it taped up about 5 ft high on a wall opposite where I regularly sit.

It flashes very bright when the phone rings, and continues flashing until the
phone is answered. This is more than enough to get my attention even when
I am listening to music through headphones or am in another room.

You will also need a length of phoneline extension cord long enough to run from the
flasher to a convenient phone wall plug, and someone who can connect the flasher
to the phone wall plug, Connecting is straightforward, but best done by someone who
knows what he/she is doing.

I be;ieve I bought my KROWN flasher online from Amazon.

I hope this helps.