Helix 9 gimbal knob

I had one come of my Helix 9. Humminbird said they do not sell replacements, unless I buy the entire bracket. Any ideas?

https://www.rammount.com/part/RAP-S-KNOBGU

Maybe these will work

Might call em back and see if you get a different representative and answee, they have sold em in the past for about $15

They are a 10-24 threaded knob. I bought a knob at Lowe's for less than $3. Thanks everyone.