I'll post this as an answer, but it's really a frame challenge.

As manassehkatz-Moving to Codidact correctly notes, many people just reach for towel bars and use them as grab bars. I like doing that too. So when I installed my last set, I used grab bars in place of towel bars, making sure each end was fastened with actual screws into studs:

(image from Google Images)

That last installation (four different bars in a master bath) was in 2008. Each is still secure and firmly attached to the wall. It's a pleasure to hold such a large and confidence-inspiring bar.

I'll post this as an answer, but it's really a frame challenge.

As manassehkatz-Moving to Codidact correctly notes, many people just reach for towel bars and use them as grab bars. I like doing that too. So when I installed my last set, I used grab bars in place of towel bars, making sure each end was fastened with actual screws into studs:

(image from Google Images)

That last installation (four different bars in a master bath) was in 2008. Each is still secure and firmly attached. It's a pleasure to hold such a large and confidence-inspiring bar.